What is the list of supported languages/locales on Android? [closed]

Question

Updated list as of Android 5.1:

af_ [Afrikaans]
af_NA [Afrikaans (Namibia)]
af_ZA [Afrikaans (South Africa)]
agq_ [Aghem]
agq_CM [Aghem (Cameroon)]
ak_ [Akan]
ak_GH [Akan (Ghana)]
am_ [Amharic]
am_ET [Amharic (Ethiopia)]
ar_ [Arabic]
ar_001 [Arabic (World)]
ar_AE [Arabic (United Arab Emirates)]
ar_BH [Arabic (Bahrain)]
ar_DJ [Arabic (Djibouti)]
ar_DZ [Arabic (Algeria)]
ar_EG [Arabic (Egypt)]
ar_EH [Arabic (Western Sahara)]
ar_ER [Arabic (Eritrea)]
ar_IL [Arabic (Israel)]
ar_IQ [Arabic (Iraq)]
ar_JO [Arabic (Jordan)]
ar_KM [Arabic (Comoros)]
ar_KW [Arabic (Kuwait)]
ar_LB [Arabic (Lebanon)]
ar_LY [Arabic (Libya)]
ar_MA [Arabic (Morocco)]
ar_MR [Arabic (Mauritania)]
ar_OM [Arabic (Oman)]
ar_PS [Arabic (Palestine)]
ar_QA [Arabic (Qatar)]
ar_SA [Arabic (Saudi Arabia)]
ar_SD [Arabic (Sudan)]
ar_SO [Arabic (Somalia)]
ar_SS [Arabic (South Sudan)]
ar_SY [Arabic (Syria)]
ar_TD [Arabic (Chad)]
ar_TN [Arabic (Tunisia)]
ar_YE [Arabic (Yemen)]
as_ [Assamese]
as_IN [Assamese (India)]
asa_ [Asu]
asa_TZ [Asu (Tanzania)]
az_ [Azerbaijani]
az_ [Azerbaijani (Cyrillic)]
az_AZ [Azerbaijani (Cyrillic,Azerbaijan)]
az_ [Azerbaijani (Latin)]
az_AZ [Azerbaijani (Latin,Azerbaijan)]
bas_ [Basaa]
bas_CM [Basaa (Cameroon)]
be_ [Belarusian]
be_BY [Belarusian (Belarus)]
bem_ [Bemba]
bem_ZM [Bemba (Zambia)]
bez_ [Bena]
bez_TZ [Bena (Tanzania)]
bg_ [Bulgarian]
bg_BG [Bulgarian (Bulgaria)]
bm_ [Bambara]
bm_ML [Bambara (Mali)]
bn_ [Bengali]
bn_BD [Bengali (Bangladesh)]
bn_IN [Bengali (India)]
bo_ [Tibetan]
bo_CN [Tibetan (China)]
bo_IN [Tibetan (India)]
br_ [Breton]
br_FR [Breton (France)]
brx_ [Bodo]
brx_IN [Bodo (India)]
bs_ [Bosnian]
bs_ [Bosnian (Cyrillic)]
bs_BA [Bosnian (Cyrillic,Bosnia and Herzegovina)]
bs_ [Bosnian (Latin)]
bs_BA [Bosnian (Latin,Bosnia and Herzegovina)]
ca_ [Catalan]
ca_AD [Catalan (Andorra)]
ca_ES [Catalan (Spain)]
ca_FR [Catalan (France)]
ca_IT [Catalan (Italy)]
cgg_ [Chiga]
cgg_UG [Chiga (Uganda)]
chr_ [Cherokee]
chr_US [Cherokee (United States)]
cs_ [Czech]
cs_CZ [Czech (Czech Republic)]
cy_ [Welsh]
cy_GB [Welsh (United Kingdom)]
da_ [Danish]
da_DK [Danish (Denmark)]
da_GL [Danish (Greenland)]
dav_ [Taita]
dav_KE [Taita (Kenya)]
de_ [German]
de_AT [German (Austria)]
de_BE [German (Belgium)]
de_CH [German (Switzerland)]
de_DE [German (Germany)]
de_LI [German (Liechtenstein)]
de_LU [German (Luxembourg)]
dje_ [Zarma]
dje_NE [Zarma (Niger)]
dua_ [Duala]
dua_CM [Duala (Cameroon)]
dyo_ [Jola-Fonyi]
dyo_SN [Jola-Fonyi (Senegal)]
dz_ [Dzongkha]
dz_BT [Dzongkha (Bhutan)]
ebu_ [Embu]
ebu_KE [Embu (Kenya)]
ee_ [Ewe]
ee_GH [Ewe (Ghana)]
ee_TG [Ewe (Togo)]
el_ [Greek]
el_CY [Greek (Cyprus)]
el_GR [Greek (Greece)]
en_ [English]
en_001 [English (World)]
en_150 [English (Europe)]
en_AG [English (Antigua and Barbuda)]
en_AI [English (Anguilla)]
en_AS [English (American Samoa)]
en_AU [English (Australia)]
en_BB [English (Barbados)]
en_BE [English (Belgium)]
en_BM [English (Bermuda)]
en_BS [English (Bahamas)]
en_BW [English (Botswana)]
en_BZ [English (Belize)]
en_CA [English (Canada)]
en_CC [English (Cocos (Keeling) Islands)]
en_CK [English (Cook Islands)]
en_CM [English (Cameroon)]
en_CX [English (Christmas Island)]
en_DG [English (Diego Garcia)]
en_DM [English (Dominica)]
en_ER [English (Eritrea)]
en_FJ [English (Fiji)]
en_FK [English (Falkland Islands (Islas Malvinas))]
en_FM [English (Micronesia)]
en_GB [English (United Kingdom)]
en_GD [English (Grenada)]
en_GG [English (Guernsey)]
en_GH [English (Ghana)]
en_GI [English (Gibraltar)]
en_GM [English (Gambia)]
en_GU [English (Guam)]
en_GY [English (Guyana)]
en_HK [English (Hong Kong)]
en_IE [English (Ireland)]
en_IM [English (Isle of Man)]
en_IN [English (India)]
en_IO [English (British Indian Ocean Territory)]
en_JE [English (Jersey)]
en_JM [English (Jamaica)]
en_KE [English (Kenya)]
en_KI [English (Kiribati)]
en_KN [English (Saint Kitts and Nevis)]
en_KY [English (Cayman Islands)]
en_LC [English (Saint Lucia)]
en_LR [English (Liberia)]
en_LS [English (Lesotho)]
en_MG [English (Madagascar)]
en_MH [English (Marshall Islands)]
en_MO [English (Macau)]
en_MP [English (Northern Mariana Islands)]
en_MS [English (Montserrat)]
en_MT [English (Malta)]
en_MU [English (Mauritius)]
en_MW [English (Malawi)]
en_NA [English (Namibia)]
en_NF [English (Norfolk Island)]
en_NG [English (Nigeria)]
en_NR [English (Nauru)]
en_NU [English (Niue)]
en_NZ [English (New Zealand)]
en_PG [English (Papua New Guinea)]
en_PH [English (Philippines)]
en_PK [English (Pakistan)]
en_PN [English (Pitcairn Islands)]
en_PR [English (Puerto Rico)]
en_PW [English (Palau)]
en_RW [English (Rwanda)]
en_SB [English (Solomon Islands)]
en_SC [English (Seychelles)]
en_SD [English (Sudan)]
en_SG [English (Singapore)]
en_SH [English (Saint Helena)]
en_SL [English (Sierra Leone)]
en_SS [English (South Sudan)]
en_SX [English (Sint Maarten)]
en_SZ [English (Swaziland)]
en_TC [English (Turks and Caicos Islands)]
en_TK [English (Tokelau)]
en_TO [English (Tonga)]
en_TT [English (Trinidad and Tobago)]
en_TV [English (Tuvalu)]
en_TZ [English (Tanzania)]
en_UG [English (Uganda)]
en_UM [English (U.S. Outlying Islands)]
en_US [English (United States)]
en_US [English (United States,Computer)]
en_VC [English (St. Vincent & Grenadines)]
en_VG [English (British Virgin Islands)]
en_VI [English (U.S. Virgin Islands)]
en_VU [English (Vanuatu)]
en_WS [English (Samoa)]
en_ZA [English (South Africa)]
en_ZM [English (Zambia)]
en_ZW [English (Zimbabwe)]
eo_ [Esperanto]
es_ [Spanish]
es_419 [Spanish (Latin America)]
es_AR [Spanish (Argentina)]
es_BO [Spanish (Bolivia)]
es_CL [Spanish (Chile)]
es_CO [Spanish (Colombia)]
es_CR [Spanish (Costa Rica)]
es_CU [Spanish (Cuba)]
es_DO [Spanish (Dominican Republic)]
es_EA [Spanish (Ceuta and Melilla)]
es_EC [Spanish (Ecuador)]
es_ES [Spanish (Spain)]
es_GQ [Spanish (Equatorial Guinea)]
es_GT [Spanish (Guatemala)]
es_HN [Spanish (Honduras)]
es_IC [Spanish (Canary Islands)]
es_MX [Spanish (Mexico)]
es_NI [Spanish (Nicaragua)]
es_PA [Spanish (Panama)]
es_PE [Spanish (Peru)]
es_PH [Spanish (Philippines)]
es_PR [Spanish (Puerto Rico)]
es_PY [Spanish (Paraguay)]
es_SV [Spanish (El Salvador)]
es_US [Spanish (United States)]
es_UY [Spanish (Uruguay)]
es_VE [Spanish (Venezuela)]
et_ [Estonian]
et_EE [Estonian (Estonia)]
eu_ [Basque]
eu_ES [Basque (Spain)]
ewo_ [Ewondo]
ewo_CM [Ewondo (Cameroon)]
fa_ [Persian]
fa_AF [Persian (Afghanistan)]
fa_IR [Persian (Iran)]
ff_ [Fulah]
ff_SN [Fulah (Senegal)]
fi_ [Finnish]
fi_FI [Finnish (Finland)]
fil_ [Filipino]
fil_PH [Filipino (Philippines)]
fo_ [Faroese]
fo_FO [Faroese (Faroe Islands)]
fr_ [French]
fr_BE [French (Belgium)]
fr_BF [French (Burkina Faso)]
fr_BI [French (Burundi)]
fr_BJ [French (Benin)]
fr_BL [French (Saint Barthélemy)]
fr_CA [French (Canada)]
fr_CD [French (Congo (DRC))]
fr_CF [French (Central African Republic)]
fr_CG [French (Congo (Republic))]
fr_CH [French (Switzerland)]
fr_CI [French (Côte d’Ivoire)]
fr_CM [French (Cameroon)]
fr_DJ [French (Djibouti)]
fr_DZ [French (Algeria)]
fr_FR [French (France)]
fr_GA [French (Gabon)]
fr_GF [French (French Guiana)]
fr_GN [French (Guinea)]
fr_GP [French (Guadeloupe)]
fr_GQ [French (Equatorial Guinea)]
fr_HT [French (Haiti)]
fr_KM [French (Comoros)]
fr_LU [French (Luxembourg)]
fr_MA [French (Morocco)]
fr_MC [French (Monaco)]
fr_MF [French (Saint Martin)]
fr_MG [French (Madagascar)]
fr_ML [French (Mali)]
fr_MQ [French (Martinique)]
fr_MR [French (Mauritania)]
fr_MU [French (Mauritius)]
fr_NC [French (New Caledonia)]
fr_NE [French (Niger)]
fr_PF [French (French Polynesia)]
fr_PM [French (Saint Pierre and Miquelon)]
fr_RE [French (Réunion)]
fr_RW [French (Rwanda)]
fr_SC [French (Seychelles)]
fr_SN [French (Senegal)]
fr_SY [French (Syria)]
fr_TD [French (Chad)]
fr_TG [French (Togo)]
fr_TN [French (Tunisia)]
fr_VU [French (Vanuatu)]
fr_WF [French (Wallis and Futuna)]
fr_YT [French (Mayotte)]
ga_ [Irish]
ga_IE [Irish (Ireland)]
gl_ [Galician]
gl_ES [Galician (Spain)]
gsw_ [Swiss German]
gsw_CH [Swiss German (Switzerland)]
gsw_LI [Swiss German (Liechtenstein)]
gu_ [Gujarati]
gu_IN [Gujarati (India)]
guz_ [Gusii]
guz_KE [Gusii (Kenya)]
gv_ [Manx]
gv_IM [Manx (Isle of Man)]
ha_ [Hausa]
ha_ [Hausa (Latin)]
ha_GH [Hausa (Latin,Ghana)]
ha_NE [Hausa (Latin,Niger)]
ha_NG [Hausa (Latin,Nigeria)]
haw_ [Hawaiian]
haw_US [Hawaiian (United States)]
iw_ [Hebrew]
iw_IL [Hebrew (Israel)]
hi_ [Hindi]
hi_IN [Hindi (India)]
hr_ [Croatian]
hr_BA [Croatian (Bosnia and Herzegovina)]
hr_HR [Croatian (Croatia)]
hu_ [Hungarian]
hu_HU [Hungarian (Hungary)]
hy_ [Armenian]
hy_AM [Armenian (Armenia)]
in_ [Indonesian]
in_ID [Indonesian (Indonesia)]
ig_ [Igbo]
ig_NG [Igbo (Nigeria)]
ii_ [Sichuan Yi]
ii_CN [Sichuan Yi (China)]
is_ [Icelandic]
is_IS [Icelandic (Iceland)]
it_ [Italian]
it_CH [Italian (Switzerland)]
it_IT [Italian (Italy)]
it_SM [Italian (San Marino)]
ja_ [Japanese]
ja_JP [Japanese (Japan)]
jgo_ [Ngomba]
jgo_CM [Ngomba (Cameroon)]
jmc_ [Machame]
jmc_TZ [Machame (Tanzania)]
ka_ [Georgian]
ka_GE [Georgian (Georgia)]
kab_ [Kabyle]
kab_DZ [Kabyle (Algeria)]
kam_ [Kamba]
kam_KE [Kamba (Kenya)]
kde_ [Makonde]
kde_TZ [Makonde (Tanzania)]
kea_ [Kabuverdianu]
kea_CV [Kabuverdianu (Cape Verde)]
khq_ [Koyra Chiini]
khq_ML [Koyra Chiini (Mali)]
ki_ [Kikuyu]
ki_KE [Kikuyu (Kenya)]
kk_ [Kazakh]
kk_ [Kazakh (Cyrillic)]
kk_KZ [Kazakh (Cyrillic,Kazakhstan)]
kkj_ [Kako]
kkj_CM [Kako (Cameroon)]
kl_ [Kalaallisut]
kl_GL [Kalaallisut (Greenland)]
kln_ [Kalenjin]
kln_KE [Kalenjin (Kenya)]
km_ [Khmer]
km_KH [Khmer (Cambodia)]
kn_ [Kannada]
kn_IN [Kannada (India)]
ko_ [Korean]
ko_KP [Korean (North Korea)]
ko_KR [Korean (South Korea)]
kok_ [Konkani]
kok_IN [Konkani (India)]
ks_ [Kashmiri]
ks_ [Kashmiri (Arabic)]
ks_IN [Kashmiri (Arabic,India)]
ksb_ [Shambala]
ksb_TZ [Shambala (Tanzania)]
ksf_ [Bafia]
ksf_CM [Bafia (Cameroon)]
kw_ [Cornish]
kw_GB [Cornish (United Kingdom)]
ky_ [Kyrgyz]
ky_ [Kyrgyz (Cyrillic)]
ky_KG [Kyrgyz (Cyrillic,Kyrgyzstan)]
lag_ [Langi]
lag_TZ [Langi (Tanzania)]
lg_ [Ganda]
lg_UG [Ganda (Uganda)]
lkt_ [Lakota]
lkt_US [Lakota (United States)]
ln_ [Lingala]
ln_AO [Lingala (Angola)]
ln_CD [Lingala (Congo (DRC))]
ln_CF [Lingala (Central African Republic)]
ln_CG [Lingala (Congo (Republic))]
lo_ [Lao]
lo_LA [Lao (Laos)]
lt_ [Lithuanian]
lt_LT [Lithuanian (Lithuania)]
lu_ [Luba-Katanga]
lu_CD [Luba-Katanga (Congo (DRC))]
luo_ [Luo]
luo_KE [Luo (Kenya)]
luy_ [Luyia]
luy_KE [Luyia (Kenya)]
lv_ [Latvian]
lv_LV [Latvian (Latvia)]
mas_ [Masai]
mas_KE [Masai (Kenya)]
mas_TZ [Masai (Tanzania)]
mer_ [Meru]
mer_KE [Meru (Kenya)]
mfe_ [Morisyen]
mfe_MU [Morisyen (Mauritius)]
mg_ [Malagasy]
mg_MG [Malagasy (Madagascar)]
mgh_ [Makhuwa-Meetto]
mgh_MZ [Makhuwa-Meetto (Mozambique)]
mgo_ [Meta']
mgo_CM [Meta' (Cameroon)]
mk_ [Macedonian]
mk_MK [Macedonian (Macedonia (FYROM))]
ml_ [Malayalam]
ml_IN [Malayalam (India)]
mn_ [Mongolian]
mn_ [Mongolian (Cyrillic)]
mn_MN [Mongolian (Cyrillic,Mongolia)]
mr_ [Marathi]
mr_IN [Marathi (India)]
ms_ [Malay]
ms_ [Malay (Latin)]
ms_BN [Malay (Latin,Brunei)]
ms_MY [Malay (Latin,Malaysia)]
ms_SG [Malay (Latin,Singapore)]
mt_ [Maltese]
mt_MT [Maltese (Malta)]
mua_ [Mundang]
mua_CM [Mundang (Cameroon)]
my_ [Burmese]
my_MM [Burmese (Myanmar (Burma))]
naq_ [Nama]
naq_NA [Nama (Namibia)]
nb_ [Norwegian Bokmål]
nb_NO [Norwegian Bokmål (Norway)]
nb_SJ [Norwegian Bokmål (Svalbard and Jan Mayen)]
nd_ [North Ndebele]
nd_ZW [North Ndebele (Zimbabwe)]
ne_ [Nepali]
ne_IN [Nepali (India)]
ne_NP [Nepali (Nepal)]
nl_ [Dutch]
nl_AW [Dutch (Aruba)]
nl_BE [Dutch (Belgium)]
nl_BQ [Dutch (Caribbean Netherlands)]
nl_CW [Dutch (Curaçao)]
nl_NL [Dutch (Netherlands)]
nl_SR [Dutch (Suriname)]
nl_SX [Dutch (Sint Maarten)]
nmg_ [Kwasio]
nmg_CM [Kwasio (Cameroon)]
nn_ [Norwegian Nynorsk]
nn_NO [Norwegian Nynorsk (Norway)]
nnh_ [Ngiemboon]
nnh_CM [Ngiemboon (Cameroon)]
nus_ [Nuer]
nus_SD [Nuer (Sudan)]
nyn_ [Nyankole]
nyn_UG [Nyankole (Uganda)]
om_ [Oromo]
om_ET [Oromo (Ethiopia)]
om_KE [Oromo (Kenya)]
or_ [Oriya]
or_IN [Oriya (India)]
pa_ [Punjabi]
pa_ [Punjabi (Arabic)]
pa_PK [Punjabi (Arabic,Pakistan)]
pa_ [Punjabi (Gurmukhi)]
pa_IN [Punjabi (Gurmukhi,India)]
pl_ [Polish]
pl_PL [Polish (Poland)]
ps_ [Pashto]
ps_AF [Pashto (Afghanistan)]
pt_ [Portuguese]
pt_AO [Portuguese (Angola)]
pt_BR [Portuguese (Brazil)]
pt_CV [Portuguese (Cape Verde)]
pt_GW [Portuguese (Guinea-Bissau)]
pt_MO [Portuguese (Macau)]
pt_MZ [Portuguese (Mozambique)]
pt_PT [Portuguese (Portugal)]
pt_ST [Portuguese (São Tomé and Príncipe)]
pt_TL [Portuguese (Timor-Leste)]
rm_ [Romansh]
rm_CH [Romansh (Switzerland)]
rn_ [Rundi]
rn_BI [Rundi (Burundi)]
ro_ [Romanian]
ro_MD [Romanian (Moldova)]
ro_RO [Romanian (Romania)]
rof_ [Rombo]
rof_TZ [Rombo (Tanzania)]
ru_ [Russian]
ru_BY [Russian (Belarus)]
ru_KG [Russian (Kyrgyzstan)]
ru_KZ [Russian (Kazakhstan)]
ru_MD [Russian (Moldova)]
ru_RU [Russian (Russia)]
ru_UA [Russian (Ukraine)]
rw_ [Kinyarwanda]
rw_RW [Kinyarwanda (Rwanda)]
rwk_ [Rwa]
rwk_TZ [Rwa (Tanzania)]
saq_ [Samburu]
saq_KE [Samburu (Kenya)]
sbp_ [Sangu]
sbp_TZ [Sangu (Tanzania)]
seh_ [Sena]
seh_MZ [Sena (Mozambique)]
ses_ [Koyraboro Senni]
ses_ML [Koyraboro Senni (Mali)]
sg_ [Sango]
sg_CF [Sango (Central African Republic)]
shi_ [Tachelhit]
shi_ [Tachelhit (Latin)]
shi_MA [Tachelhit (Latin,Morocco)]
shi_ [Tachelhit (Tifinagh)]
shi_MA [Tachelhit (Tifinagh,Morocco)]
si_ [Sinhala]
si_LK [Sinhala (Sri Lanka)]
sk_ [Slovak]
sk_SK [Slovak (Slovakia)]
sl_ [Slovenian]
sl_SI [Slovenian (Slovenia)]
sn_ [Shona]
sn_ZW [Shona (Zimbabwe)]
so_ [Somali]
so_DJ [Somali (Djibouti)]
so_ET [Somali (Ethiopia)]
so_KE [Somali (Kenya)]
so_SO [Somali (Somalia)]
sq_ [Albanian]
sq_AL [Albanian (Albania)]
sq_MK [Albanian (Macedonia (FYROM))]
sq_XK [Albanian (Kosovo)]
sr_ [Serbian]
sr_ [Serbian (Cyrillic)]
sr_BA [Serbian (Cyrillic,Bosnia and Herzegovina)]
sr_ME [Serbian (Cyrillic,Montenegro)]
sr_RS [Serbian (Cyrillic,Serbia)]
sr_XK [Serbian (Cyrillic,Kosovo)]
sr_ [Serbian (Latin)]
sr_BA [Serbian (Latin,Bosnia and Herzegovina)]
sr_ME [Serbian (Latin,Montenegro)]
sr_RS [Serbian (Latin,Serbia)]
sr_XK [Serbian (Latin,Kosovo)]
sv_ [Swedish]
sv_AX [Swedish (Åland Islands)]
sv_FI [Swedish (Finland)]
sv_SE [Swedish (Sweden)]
sw_ [Swahili]
sw_KE [Swahili (Kenya)]
sw_TZ [Swahili (Tanzania)]
sw_UG [Swahili (Uganda)]
swc_ [Congo Swahili]
swc_CD [Congo Swahili (Congo (DRC))]
ta_ [Tamil]
ta_IN [Tamil (India)]
ta_LK [Tamil (Sri Lanka)]
ta_MY [Tamil (Malaysia)]
ta_SG [Tamil (Singapore)]
te_ [Telugu]
te_IN [Telugu (India)]
teo_ [Teso]
teo_KE [Teso (Kenya)]
teo_UG [Teso (Uganda)]
th_ [Thai]
th_TH [Thai (Thailand)]
ti_ [Tigrinya]
ti_ER [Tigrinya (Eritrea)]
ti_ET [Tigrinya (Ethiopia)]
to_ [Tongan]
to_TO [Tongan (Tonga)]
tr_ [Turkish]
tr_CY [Turkish (Cyprus)]
tr_TR [Turkish (Turkey)]
twq_ [Tasawaq]
twq_NE [Tasawaq (Niger)]
tzm_ [Central Atlas Tamazight]
tzm_ [Central Atlas Tamazight (Latin)]
tzm_MA [Central Atlas Tamazight (Latin,Morocco)]
ug_ [Uyghur]
ug_ [Uyghur (Arabic)]
ug_CN [Uyghur (Arabic,China)]
uk_ [Ukrainian]
uk_UA [Ukrainian (Ukraine)]
ur_ [Urdu]
ur_IN [Urdu (India)]
ur_PK [Urdu (Pakistan)]
uz_ [Uzbek]
uz_ [Uzbek (Arabic)]
uz_AF [Uzbek (Arabic,Afghanistan)]
uz_ [Uzbek (Cyrillic)]
uz_UZ [Uzbek (Cyrillic,Uzbekistan)]
uz_ [Uzbek (Latin)]
uz_UZ [Uzbek (Latin,Uzbekistan)]
vai_ [Vai]
vai_ [Vai (Latin)]
vai_LR [Vai (Latin,Liberia)]
vai_ [Vai (Vai)]
vai_LR [Vai (Vai,Liberia)]
vi_ [Vietnamese]
vi_VN [Vietnamese (Vietnam)]
vun_ [Vunjo]
vun_TZ [Vunjo (Tanzania)]
xog_ [Soga]
xog_UG [Soga (Uganda)]
yav_ [Yangben]
yav_CM [Yangben (Cameroon)]
yo_ [Yoruba]
yo_BJ [Yoruba (Benin)]
yo_NG [Yoruba (Nigeria)]
zgh_ [Standard Moroccan Tamazight]
zgh_MA [Standard Moroccan Tamazight (Morocco)]
zh_ [Chinese]
zh_ [Chinese (Simplified Han)]
zh_CN [Chinese (Simplified Han,China)]
zh_HK [Chinese (Simplified Han,Hong Kong)]
zh_MO [Chinese (Simplified Han,Macau)]
zh_SG [Chinese (Simplified Han,Singapore)]
zh_ [Chinese (Traditional Han)]
zh_HK [Chinese (Traditional Han,Hong Kong)]
zh_MO [Chinese (Traditional Han,Macau)]
zh_TW [Chinese (Traditional Han,Taiwan)]
zu_ [Zulu]
zu_ZA [Zulu (South Africa)]

Original Answer :

As of Android 5.0, all languages in BCP 47 are available for application development (they may not necessarily be available for selection in a given device's system settings, though). When using ISO 639-1 codes, the resource folder has the format values-xx... where xx is the ISO-639-1 code.

When using BCP 47 tags, the resource folder is named values-b+xxx... where xxx is the three-letter language code.

Here's the list for before Android 2.3 (Source)

Language / Locale                 Supported since version

English, US (en_US)               1.1
German, Germany (de_DE)           1.1
Chinese, PRC (zh_CN)              1.5
Chinese, Taiwan (zh_TW)           1.5
Czech, Czech Republic (cs_CZ)     1.5
Dutch, Belgium (nl_BE)            1.5
Dutch, Netherlands (nl_NL)        1.5
English, Australia (en_AU)        1.5
English, Britain (en_GB)          1.5
English, Canada (en_CA)           1.5
English, New Zealand (en_NZ)      1.5
English, Singapore(en_SG)         1.5
French, Belgium (fr_BE)           1.5
French, Canada (fr_CA)            1.5
French, France (fr_FR)            1.5
French, Switzerland (fr_CH)       1.5
German, Austria (de_AT)           1.5
German, Liechtenstein (de_LI)     1.5
German, Switzerland (de_CH)       1.5
Italian, Italy (it_IT)            1.5
Italian, Switzerland (it_CH)      1.5
Japanese (ja_JP)                  1.5
Korean (ko_KR)                    1.5
Polish (pl_PL)                    1.5
Russian (ru_RU)                   1.5
Spanish (es_ES)                   1.5
Arabic, Egypt (ar_EG)             2.3
Arabic, Israel (ar_IL)            2.3
Bulgarian, Bulgaria (bg_BG)       2.3
Catalan, Spain (ca_ES)            2.3
Croatian, Croatia (hr_HR)         2.3
Danish, Denmark(da_DK)            2.3
English, India (en_IN)            2.3
English, Ireland (en_IE)          2.3
English, Zimbabwe (en_ZA)         2.3
Finnish, Finland (fi_FI)          2.3
Greek, Greece (el_GR)             2.3
Hebrew, Israel (iw_IL)*           2.3
Hindi, India (hi_IN)              2.3
Hungarian, Hungary (hu_HU)        2.3
Indonesian, Indonesia (in_ID)*    2.3
Latvian, Latvia (lv_LV)           2.3
Lithuanian, Lithuania (lt_LT)     2.3
Norwegian-Bokmål, Norway(nb_NO)   2.3
Portuguese, Brazil (pt_BR)        2.3
Portuguese, Portugal (pt_PT)      2.3
Romanian, Romania (ro_RO)         2.3
Serbian (sr_RS)                   2.3
Slovak, Slovakia (sk_SK)          2.3
Slovenian, Slovenia (sl_SI)       2.3
Spanish, US (es_US)               2.3
Swedish, Sweden (sv_SE)           2.3
Tagalog, Philippines (tl_PH)      2.3
Thai, Thailand (th_TH)            2.3
Turkish, Turkey (tr_TR)           2.3
Ukrainian, Ukraine (uk_UA)        2.3
Vietnamese, Vietnam (vi_VN)       2.3

*Note that Java uses several deprecated two-letter codes. The Hebrew (“he”) >language code is rewritten as “iw”, Indonesian (“id”) as “in”, and Yiddish (“yi”) as “ji”. This rewriting happens even if you construct your own Locale object, not just for instances returned by the various lookup methods. See also https://issuetracker.google.com/issues/36908826.

List of locales supported as of API 22 (Android 5.1). Obtained from a Nexus 5 with locale set to "English (United States)" (locale affects the DisplayName output).

for (Locale locale : Locale.getAvailableLocales()) {
    Log.d("LOCALES", locale.getLanguage() + "_" + locale.getCountry() + " [" + locale.getDisplayName() + "]");
}


    af_ [Afrikaans]
    af_NA [Afrikaans (Namibia)]
    af_ZA [Afrikaans (South Africa)]
    agq_ [Aghem]
    agq_CM [Aghem (Cameroon)]
    ak_ [Akan]
    ak_GH [Akan (Ghana)]
    am_ [Amharic]
    am_ET [Amharic (Ethiopia)]
    ar_ [Arabic]
    ar_001 [Arabic (World)]
    ar_AE [Arabic (United Arab Emirates)]
    ar_BH [Arabic (Bahrain)]
    ar_DJ [Arabic (Djibouti)]
    ar_DZ [Arabic (Algeria)]
    ar_EG [Arabic (Egypt)]
    ar_EH [Arabic (Western Sahara)]
    ar_ER [Arabic (Eritrea)]
    ar_IL [Arabic (Israel)]
    ar_IQ [Arabic (Iraq)]
    ar_JO [Arabic (Jordan)]
    ar_KM [Arabic (Comoros)]
    ar_KW [Arabic (Kuwait)]
    ar_LB [Arabic (Lebanon)]
    ar_LY [Arabic (Libya)]
    ar_MA [Arabic (Morocco)]
    ar_MR [Arabic (Mauritania)]
    ar_OM [Arabic (Oman)]
    ar_PS [Arabic (Palestine)]
    ar_QA [Arabic (Qatar)]
    ar_SA [Arabic (Saudi Arabia)]
    ar_SD [Arabic (Sudan)]
    ar_SO [Arabic (Somalia)]
    ar_SS [Arabic (South Sudan)]
    ar_SY [Arabic (Syria)]
    ar_TD [Arabic (Chad)]
    ar_TN [Arabic (Tunisia)]
    ar_YE [Arabic (Yemen)]
    as_ [Assamese]
    as_IN [Assamese (India)]
    asa_ [Asu]
    asa_TZ [Asu (Tanzania)]
    az_ [Azerbaijani]
    az_ [Azerbaijani (Cyrillic)]
    az_AZ [Azerbaijani (Cyrillic,Azerbaijan)]
    az_ [Azerbaijani (Latin)]
    az_AZ [Azerbaijani (Latin,Azerbaijan)]
    bas_ [Basaa]
    bas_CM [Basaa (Cameroon)]
    be_ [Belarusian]
    be_BY [Belarusian (Belarus)]
    bem_ [Bemba]
    bem_ZM [Bemba (Zambia)]
    bez_ [Bena]
    bez_TZ [Bena (Tanzania)]
    bg_ [Bulgarian]
    bg_BG [Bulgarian (Bulgaria)]
    bm_ [Bambara]
    bm_ML [Bambara (Mali)]
    bn_ [Bengali]
    bn_BD [Bengali (Bangladesh)]
    bn_IN [Bengali (India)]
    bo_ [Tibetan]
    bo_CN [Tibetan (China)]
    bo_IN [Tibetan (India)]
    br_ [Breton]
    br_FR [Breton (France)]
    brx_ [Bodo]
    brx_IN [Bodo (India)]
    bs_ [Bosnian]
    bs_ [Bosnian (Cyrillic)]
    bs_BA [Bosnian (Cyrillic,Bosnia and Herzegovina)]
    bs_ [Bosnian (Latin)]
    bs_BA [Bosnian (Latin,Bosnia and Herzegovina)]
    ca_ [Catalan]
    ca_AD [Catalan (Andorra)]
    ca_ES [Catalan (Spain)]
    ca_FR [Catalan (France)]
    ca_IT [Catalan (Italy)]
    cgg_ [Chiga]
    cgg_UG [Chiga (Uganda)]
    chr_ [Cherokee]
    chr_US [Cherokee (United States)]
    cs_ [Czech]
    cs_CZ [Czech (Czech Republic)]
    cy_ [Welsh]
    cy_GB [Welsh (United Kingdom)]
    da_ [Danish]
    da_DK [Danish (Denmark)]
    da_GL [Danish (Greenland)]
    dav_ [Taita]
    dav_KE [Taita (Kenya)]
    de_ [German]
    de_AT [German (Austria)]
    de_BE [German (Belgium)]
    de_CH [German (Switzerland)]
    de_DE [German (Germany)]
    de_LI [German (Liechtenstein)]
    de_LU [German (Luxembourg)]
    dje_ [Zarma]
    dje_NE [Zarma (Niger)]
    dua_ [Duala]
    dua_CM [Duala (Cameroon)]
    dyo_ [Jola-Fonyi]
    dyo_SN [Jola-Fonyi (Senegal)]
    dz_ [Dzongkha]
    dz_BT [Dzongkha (Bhutan)]
    ebu_ [Embu]
    ebu_KE [Embu (Kenya)]
    ee_ [Ewe]
    ee_GH [Ewe (Ghana)]
    ee_TG [Ewe (Togo)]
    el_ [Greek]
    el_CY [Greek (Cyprus)]
    el_GR [Greek (Greece)]
    en_ [English]
    en_001 [English (World)]
    en_150 [English (Europe)]
    en_AG [English (Antigua and Barbuda)]
    en_AI [English (Anguilla)]
    en_AS [English (American Samoa)]
    en_AU [English (Australia)]
    en_BB [English (Barbados)]
    en_BE [English (Belgium)]
    en_BM [English (Bermuda)]
    en_BS [English (Bahamas)]
    en_BW [English (Botswana)]
    en_BZ [English (Belize)]
    en_CA [English (Canada)]
    en_CC [English (Cocos (Keeling) Islands)]
    en_CK [English (Cook Islands)]
    en_CM [English (Cameroon)]
    en_CX [English (Christmas Island)]
    en_DG [English (Diego Garcia)]
    en_DM [English (Dominica)]
    en_ER [English (Eritrea)]
    en_FJ [English (Fiji)]
    en_FK [English (Falkland Islands (Islas Malvinas))]
    en_FM [English (Micronesia)]
    en_GB [English (United Kingdom)]
    en_GD [English (Grenada)]
    en_GG [English (Guernsey)]
    en_GH [English (Ghana)]
    en_GI [English (Gibraltar)]
    en_GM [English (Gambia)]
    en_GU [English (Guam)]
    en_GY [English (Guyana)]
    en_HK [English (Hong Kong)]
    en_IE [English (Ireland)]
    en_IM [English (Isle of Man)]
    en_IN [English (India)]
    en_IO [English (British Indian Ocean Territory)]
    en_JE [English (Jersey)]
    en_JM [English (Jamaica)]
    en_KE [English (Kenya)]
    en_KI [English (Kiribati)]
    en_KN [English (Saint Kitts and Nevis)]
    en_KY [English (Cayman Islands)]
    en_LC [English (Saint Lucia)]
    en_LR [English (Liberia)]
    en_LS [English (Lesotho)]
    en_MG [English (Madagascar)]
    en_MH [English (Marshall Islands)]
    en_MO [English (Macau)]
    en_MP [English (Northern Mariana Islands)]
    en_MS [English (Montserrat)]
    en_MT [English (Malta)]
    en_MU [English (Mauritius)]
    en_MW [English (Malawi)]
    en_NA [English (Namibia)]
    en_NF [English (Norfolk Island)]
    en_NG [English (Nigeria)]
    en_NR [English (Nauru)]
    en_NU [English (Niue)]
    en_NZ [English (New Zealand)]
    en_PG [English (Papua New Guinea)]
    en_PH [English (Philippines)]
    en_PK [English (Pakistan)]
    en_PN [English (Pitcairn Islands)]
    en_PR [English (Puerto Rico)]
    en_PW [English (Palau)]
    en_RW [English (Rwanda)]
    en_SB [English (Solomon Islands)]
    en_SC [English (Seychelles)]
    en_SD [English (Sudan)]
    en_SG [English (Singapore)]
    en_SH [English (Saint Helena)]
    en_SL [English (Sierra Leone)]
    en_SS [English (South Sudan)]
    en_SX [English (Sint Maarten)]
    en_SZ [English (Swaziland)]
    en_TC [English (Turks and Caicos Islands)]
    en_TK [English (Tokelau)]
    en_TO [English (Tonga)]
    en_TT [English (Trinidad and Tobago)]
    en_TV [English (Tuvalu)]
    en_TZ [English (Tanzania)]
    en_UG [English (Uganda)]
    en_UM [English (U.S. Outlying Islands)]
    en_US [English (United States)]
    en_US [English (United States,Computer)]
    en_VC [English (St. Vincent & Grenadines)]
    en_VG [English (British Virgin Islands)]
    en_VI [English (U.S. Virgin Islands)]
    en_VU [English (Vanuatu)]
    en_WS [English (Samoa)]
    en_ZA [English (South Africa)]
    en_ZM [English (Zambia)]
    en_ZW [English (Zimbabwe)]
    eo_ [Esperanto]
    es_ [Spanish]
    es_419 [Spanish (Latin America)]
    es_AR [Spanish (Argentina)]
    es_BO [Spanish (Bolivia)]
    es_CL [Spanish (Chile)]
    es_CO [Spanish (Colombia)]
    es_CR [Spanish (Costa Rica)]
    es_CU [Spanish (Cuba)]
    es_DO [Spanish (Dominican Republic)]
    es_EA [Spanish (Ceuta and Melilla)]
    es_EC [Spanish (Ecuador)]
    es_ES [Spanish (Spain)]
    es_GQ [Spanish (Equatorial Guinea)]
    es_GT [Spanish (Guatemala)]
    es_HN [Spanish (Honduras)]
    es_IC [Spanish (Canary Islands)]
    es_MX [Spanish (Mexico)]
    es_NI [Spanish (Nicaragua)]
    es_PA [Spanish (Panama)]
    es_PE [Spanish (Peru)]
    es_PH [Spanish (Philippines)]
    es_PR [Spanish (Puerto Rico)]
    es_PY [Spanish (Paraguay)]
    es_SV [Spanish (El Salvador)]
    es_US [Spanish (United States)]
    es_UY [Spanish (Uruguay)]
    es_VE [Spanish (Venezuela)]
    et_ [Estonian]
    et_EE [Estonian (Estonia)]
    eu_ [Basque]
    eu_ES [Basque (Spain)]
    ewo_ [Ewondo]
    ewo_CM [Ewondo (Cameroon)]
    fa_ [Persian]
    fa_AF [Persian (Afghanistan)]
    fa_IR [Persian (Iran)]
    ff_ [Fulah]
    ff_SN [Fulah (Senegal)]
    fi_ [Finnish]
    fi_FI [Finnish (Finland)]
    fil_ [Filipino]
    fil_PH [Filipino (Philippines)]
    fo_ [Faroese]
    fo_FO [Faroese (Faroe Islands)]
    fr_ [French]
    fr_BE [French (Belgium)]
    fr_BF [French (Burkina Faso)]
    fr_BI [French (Burundi)]
    fr_BJ [French (Benin)]
    fr_BL [French (Saint Barthélemy)]
    fr_CA [French (Canada)]
    fr_CD [French (Congo (DRC))]
    fr_CF [French (Central African Republic)]
    fr_CG [French (Congo (Republic))]
    fr_CH [French (Switzerland)]
    fr_CI [French (Côte d’Ivoire)]
    fr_CM [French (Cameroon)]
    fr_DJ [French (Djibouti)]
    fr_DZ [French (Algeria)]
    fr_FR [French (France)]
    fr_GA [French (Gabon)]
    fr_GF [French (French Guiana)]
    fr_GN [French (Guinea)]
    fr_GP [French (Guadeloupe)]
    fr_GQ [French (Equatorial Guinea)]
    fr_HT [French (Haiti)]
    fr_KM [French (Comoros)]
    fr_LU [French (Luxembourg)]
    fr_MA [French (Morocco)]
    fr_MC [French (Monaco)]
    fr_MF [French (Saint Martin)]
    fr_MG [French (Madagascar)]
    fr_ML [French (Mali)]
    fr_MQ [French (Martinique)]
    fr_MR [French (Mauritania)]
    fr_MU [French (Mauritius)]
    fr_NC [French (New Caledonia)]
    fr_NE [French (Niger)]
    fr_PF [French (French Polynesia)]
    fr_PM [French (Saint Pierre and Miquelon)]
    fr_RE [French (Réunion)]
    fr_RW [French (Rwanda)]
    fr_SC [French (Seychelles)]
    fr_SN [French (Senegal)]
    fr_SY [French (Syria)]
    fr_TD [French (Chad)]
    fr_TG [French (Togo)]
    fr_TN [French (Tunisia)]
    fr_VU [French (Vanuatu)]
    fr_WF [French (Wallis and Futuna)]
    fr_YT [French (Mayotte)]
    ga_ [Irish]
    ga_IE [Irish (Ireland)]
    gl_ [Galician]
    gl_ES [Galician (Spain)]
    gsw_ [Swiss German]
    gsw_CH [Swiss German (Switzerland)]
    gsw_LI [Swiss German (Liechtenstein)]
    gu_ [Gujarati]
    gu_IN [Gujarati (India)]
    guz_ [Gusii]
    guz_KE [Gusii (Kenya)]
    gv_ [Manx]
    gv_IM [Manx (Isle of Man)]
    ha_ [Hausa]
    ha_ [Hausa (Latin)]
    ha_GH [Hausa (Latin,Ghana)]
    ha_NE [Hausa (Latin,Niger)]
    ha_NG [Hausa (Latin,Nigeria)]
    haw_ [Hawaiian]
    haw_US [Hawaiian (United States)]
    iw_ [Hebrew]
    iw_IL [Hebrew (Israel)]
    hi_ [Hindi]
    hi_IN [Hindi (India)]
    hr_ [Croatian]
    hr_BA [Croatian (Bosnia and Herzegovina)]
    hr_HR [Croatian (Croatia)]
    hu_ [Hungarian]
    hu_HU [Hungarian (Hungary)]
    hy_ [Armenian]
    hy_AM [Armenian (Armenia)]
    in_ [Indonesian]
    in_ID [Indonesian (Indonesia)]
    ig_ [Igbo]
    ig_NG [Igbo (Nigeria)]
    ii_ [Sichuan Yi]
    ii_CN [Sichuan Yi (China)]
    is_ [Icelandic]
    is_IS [Icelandic (Iceland)]
    it_ [Italian]
    it_CH [Italian (Switzerland)]
    it_IT [Italian (Italy)]
    it_SM [Italian (San Marino)]
    ja_ [Japanese]
    ja_JP [Japanese (Japan)]
    jgo_ [Ngomba]
    jgo_CM [Ngomba (Cameroon)]
    jmc_ [Machame]
    jmc_TZ [Machame (Tanzania)]
    ka_ [Georgian]
    ka_GE [Georgian (Georgia)]
    kab_ [Kabyle]
    kab_DZ [Kabyle (Algeria)]
    kam_ [Kamba]
    kam_KE [Kamba (Kenya)]
    kde_ [Makonde]
    kde_TZ [Makonde (Tanzania)]
    kea_ [Kabuverdianu]
    kea_CV [Kabuverdianu (Cape Verde)]
    khq_ [Koyra Chiini]
    khq_ML [Koyra Chiini (Mali)]
    ki_ [Kikuyu]
    ki_KE [Kikuyu (Kenya)]
    kk_ [Kazakh]
    kk_ [Kazakh (Cyrillic)]
    kk_KZ [Kazakh (Cyrillic,Kazakhstan)]
    kkj_ [Kako]
    kkj_CM [Kako (Cameroon)]
    kl_ [Kalaallisut]
    kl_GL [Kalaallisut (Greenland)]
    kln_ [Kalenjin]
    kln_KE [Kalenjin (Kenya)]
    km_ [Khmer]
    km_KH [Khmer (Cambodia)]
    kn_ [Kannada]
    kn_IN [Kannada (India)]
    ko_ [Korean]
    ko_KP [Korean (North Korea)]
    ko_KR [Korean (South Korea)]
    kok_ [Konkani]
    kok_IN [Konkani (India)]
    ks_ [Kashmiri]
    ks_ [Kashmiri (Arabic)]
    ks_IN [Kashmiri (Arabic,India)]
    ksb_ [Shambala]
    ksb_TZ [Shambala (Tanzania)]
    ksf_ [Bafia]
    ksf_CM [Bafia (Cameroon)]
    kw_ [Cornish]
    kw_GB [Cornish (United Kingdom)]
    ky_ [Kyrgyz]
    ky_ [Kyrgyz (Cyrillic)]
    ky_KG [Kyrgyz (Cyrillic,Kyrgyzstan)]
    lag_ [Langi]
    lag_TZ [Langi (Tanzania)]
    lg_ [Ganda]
    lg_UG [Ganda (Uganda)]
    lkt_ [Lakota]
    lkt_US [Lakota (United States)]
    ln_ [Lingala]
    ln_AO [Lingala (Angola)]
    ln_CD [Lingala (Congo (DRC))]
    ln_CF [Lingala (Central African Republic)]
    ln_CG [Lingala (Congo (Republic))]
    lo_ [Lao]
    lo_LA [Lao (Laos)]
    lt_ [Lithuanian]
    lt_LT [Lithuanian (Lithuania)]
    lu_ [Luba-Katanga]
    lu_CD [Luba-Katanga (Congo (DRC))]
    luo_ [Luo]
    luo_KE [Luo (Kenya)]
    luy_ [Luyia]
    luy_KE [Luyia (Kenya)]
    lv_ [Latvian]
    lv_LV [Latvian (Latvia)]
    mas_ [Masai]
    mas_KE [Masai (Kenya)]
    mas_TZ [Masai (Tanzania)]
    mer_ [Meru]
    mer_KE [Meru (Kenya)]
    mfe_ [Morisyen]
    mfe_MU [Morisyen (Mauritius)]
    mg_ [Malagasy]
    mg_MG [Malagasy (Madagascar)]
    mgh_ [Makhuwa-Meetto]
    mgh_MZ [Makhuwa-Meetto (Mozambique)]
    mgo_ [Meta']
    mgo_CM [Meta' (Cameroon)]
    mk_ [Macedonian]
    mk_MK [Macedonian (Macedonia (FYROM))]
    ml_ [Malayalam]
    ml_IN [Malayalam (India)]
    mn_ [Mongolian]
    mn_ [Mongolian (Cyrillic)]
    mn_MN [Mongolian (Cyrillic,Mongolia)]
    mr_ [Marathi]
    mr_IN [Marathi (India)]
    ms_ [Malay]
    ms_ [Malay (Latin)]
    ms_BN [Malay (Latin,Brunei)]
    ms_MY [Malay (Latin,Malaysia)]
    ms_SG [Malay (Latin,Singapore)]
    mt_ [Maltese]
    mt_MT [Maltese (Malta)]
    mua_ [Mundang]
    mua_CM [Mundang (Cameroon)]
    my_ [Burmese]
    my_MM [Burmese (Myanmar (Burma))]
    naq_ [Nama]
    naq_NA [Nama (Namibia)]
    nb_ [Norwegian Bokmål]
    nb_NO [Norwegian Bokmål (Norway)]
    nb_SJ [Norwegian Bokmål (Svalbard and Jan Mayen)]
    nd_ [North Ndebele]
    nd_ZW [North Ndebele (Zimbabwe)]
    ne_ [Nepali]
    ne_IN [Nepali (India)]
    ne_NP [Nepali (Nepal)]
    nl_ [Dutch]
    nl_AW [Dutch (Aruba)]
    nl_BE [Dutch (Belgium)]
    nl_BQ [Dutch (Caribbean Netherlands)]
    nl_CW [Dutch (Curaçao)]
    nl_NL [Dutch (Netherlands)]
    nl_SR [Dutch (Suriname)]
    nl_SX [Dutch (Sint Maarten)]
    nmg_ [Kwasio]
    nmg_CM [Kwasio (Cameroon)]
    nn_ [Norwegian Nynorsk]
    nn_NO [Norwegian Nynorsk (Norway)]
    nnh_ [Ngiemboon]
    nnh_CM [Ngiemboon (Cameroon)]
    nus_ [Nuer]
    nus_SD [Nuer (Sudan)]
    nyn_ [Nyankole]
    nyn_UG [Nyankole (Uganda)]
    om_ [Oromo]
    om_ET [Oromo (Ethiopia)]
    om_KE [Oromo (Kenya)]
    or_ [Oriya]
    or_IN [Oriya (India)]
    pa_ [Punjabi]
    pa_ [Punjabi (Arabic)]
    pa_PK [Punjabi (Arabic,Pakistan)]
    pa_ [Punjabi (Gurmukhi)]
    pa_IN [Punjabi (Gurmukhi,India)]
    pl_ [Polish]
    pl_PL [Polish (Poland)]
    ps_ [Pashto]
    ps_AF [Pashto (Afghanistan)]
    pt_ [Portuguese]
    pt_AO [Portuguese (Angola)]
    pt_BR [Portuguese (Brazil)]
    pt_CV [Portuguese (Cape Verde)]
    pt_GW [Portuguese (Guinea-Bissau)]
    pt_MO [Portuguese (Macau)]
    pt_MZ [Portuguese (Mozambique)]
    pt_PT [Portuguese (Portugal)]
    pt_ST [Portuguese (São Tomé and Príncipe)]
    pt_TL [Portuguese (Timor-Leste)]
    rm_ [Romansh]
    rm_CH [Romansh (Switzerland)]
    rn_ [Rundi]
    rn_BI [Rundi (Burundi)]
    ro_ [Romanian]
    ro_MD [Romanian (Moldova)]
    ro_RO [Romanian (Romania)]
    rof_ [Rombo]
    rof_TZ [Rombo (Tanzania)]
    ru_ [Russian]
    ru_BY [Russian (Belarus)]
    ru_KG [Russian (Kyrgyzstan)]
    ru_KZ [Russian (Kazakhstan)]
    ru_MD [Russian (Moldova)]
    ru_RU [Russian (Russia)]
    ru_UA [Russian (Ukraine)]
    rw_ [Kinyarwanda]
    rw_RW [Kinyarwanda (Rwanda)]
    rwk_ [Rwa]
    rwk_TZ [Rwa (Tanzania)]
    saq_ [Samburu]
    saq_KE [Samburu (Kenya)]
    sbp_ [Sangu]
    sbp_TZ [Sangu (Tanzania)]
    seh_ [Sena]
    seh_MZ [Sena (Mozambique)]
    ses_ [Koyraboro Senni]
    ses_ML [Koyraboro Senni (Mali)]
    sg_ [Sango]
    sg_CF [Sango (Central African Republic)]
    shi_ [Tachelhit]
    shi_ [Tachelhit (Latin)]
    shi_MA [Tachelhit (Latin,Morocco)]
    shi_ [Tachelhit (Tifinagh)]
    shi_MA [Tachelhit (Tifinagh,Morocco)]
    si_ [Sinhala]
    si_LK [Sinhala (Sri Lanka)]
    sk_ [Slovak]
    sk_SK [Slovak (Slovakia)]
    sl_ [Slovenian]
    sl_SI [Slovenian (Slovenia)]
    sn_ [Shona]
    sn_ZW [Shona (Zimbabwe)]
    so_ [Somali]
    so_DJ [Somali (Djibouti)]
    so_ET [Somali (Ethiopia)]
    so_KE [Somali (Kenya)]
    so_SO [Somali (Somalia)]
    sq_ [Albanian]
    sq_AL [Albanian (Albania)]
    sq_MK [Albanian (Macedonia (FYROM))]
    sq_XK [Albanian (Kosovo)]
    sr_ [Serbian]
    sr_ [Serbian (Cyrillic)]
    sr_BA [Serbian (Cyrillic,Bosnia and Herzegovina)]
    sr_ME [Serbian (Cyrillic,Montenegro)]
    sr_RS [Serbian (Cyrillic,Serbia)]
    sr_XK [Serbian (Cyrillic,Kosovo)]
    sr_ [Serbian (Latin)]
    sr_BA [Serbian (Latin,Bosnia and Herzegovina)]
    sr_ME [Serbian (Latin,Montenegro)]
    sr_RS [Serbian (Latin,Serbia)]
    sr_XK [Serbian (Latin,Kosovo)]
    sv_ [Swedish]
    sv_AX [Swedish (Åland Islands)]
    sv_FI [Swedish (Finland)]
    sv_SE [Swedish (Sweden)]
    sw_ [Swahili]
    sw_KE [Swahili (Kenya)]
    sw_TZ [Swahili (Tanzania)]
    sw_UG [Swahili (Uganda)]
    swc_ [Congo Swahili]
    swc_CD [Congo Swahili (Congo (DRC))]
    ta_ [Tamil]
    ta_IN [Tamil (India)]
    ta_LK [Tamil (Sri Lanka)]
    ta_MY [Tamil (Malaysia)]
    ta_SG [Tamil (Singapore)]
    te_ [Telugu]
    te_IN [Telugu (India)]
    teo_ [Teso]
    teo_KE [Teso (Kenya)]
    teo_UG [Teso (Uganda)]
    th_ [Thai]
    th_TH [Thai (Thailand)]
    ti_ [Tigrinya]
    ti_ER [Tigrinya (Eritrea)]
    ti_ET [Tigrinya (Ethiopia)]
    to_ [Tongan]
    to_TO [Tongan (Tonga)]
    tr_ [Turkish]
    tr_CY [Turkish (Cyprus)]
    tr_TR [Turkish (Turkey)]
    twq_ [Tasawaq]
    twq_NE [Tasawaq (Niger)]
    tzm_ [Central Atlas Tamazight]
    tzm_ [Central Atlas Tamazight (Latin)]
    tzm_MA [Central Atlas Tamazight (Latin,Morocco)]
    ug_ [Uyghur]
    ug_ [Uyghur (Arabic)]
    ug_CN [Uyghur (Arabic,China)]
    uk_ [Ukrainian]
    uk_UA [Ukrainian (Ukraine)]
    ur_ [Urdu]
    ur_IN [Urdu (India)]
    ur_PK [Urdu (Pakistan)]
    uz_ [Uzbek]
    uz_ [Uzbek (Arabic)]
    uz_AF [Uzbek (Arabic,Afghanistan)]
    uz_ [Uzbek (Cyrillic)]
    uz_UZ [Uzbek (Cyrillic,Uzbekistan)]
    uz_ [Uzbek (Latin)]
    uz_UZ [Uzbek (Latin,Uzbekistan)]
    vai_ [Vai]
    vai_ [Vai (Latin)]
    vai_LR [Vai (Latin,Liberia)]
    vai_ [Vai (Vai)]
    vai_LR [Vai (Vai,Liberia)]
    vi_ [Vietnamese]
    vi_VN [Vietnamese (Vietnam)]
    vun_ [Vunjo]
    vun_TZ [Vunjo (Tanzania)]
    xog_ [Soga]
    xog_UG [Soga (Uganda)]
    yav_ [Yangben]
    yav_CM [Yangben (Cameroon)]
    yo_ [Yoruba]
    yo_BJ [Yoruba (Benin)]
    yo_NG [Yoruba (Nigeria)]
    zgh_ [Standard Moroccan Tamazight]
    zgh_MA [Standard Moroccan Tamazight (Morocco)]
    zh_ [Chinese]
    zh_ [Chinese (Simplified Han)]
    zh_CN [Chinese (Simplified Han,China)]
    zh_HK [Chinese (Simplified Han,Hong Kong)]
    zh_MO [Chinese (Simplified Han,Macau)]
    zh_SG [Chinese (Simplified Han,Singapore)]
    zh_ [Chinese (Traditional Han)]
    zh_HK [Chinese (Traditional Han,Hong Kong)]
    zh_MO [Chinese (Traditional Han,Macau)]
    zh_TW [Chinese (Traditional Han,Taiwan)]
    zu_ [Zulu]
    zu_ZA [Zulu (South Africa)]

The best way to see the supported list is to start up the emulator in the latest version and open the "Custom Locale" app. This will list all of the supported languages and locales for that version of Android.

Update for 4.0

Android 4.0.3 Platform

Arabic, Egypt (ar_EG)
Arabic, Israel (ar_IL)
Bulgarian, Bulgaria (bg_BG)
Catalan, Spain (ca_ES)
Chinese, PRC (zh_CN)
Chinese, Taiwan (zh_TW)
Croatian, Croatia (hr_HR)
Czech, Czech Republic (cs_CZ)
Danish, Denmark(da_DK)
Dutch, Belgium (nl_BE)
Dutch, Netherlands (nl_NL)
English, Australia (en_AU)
English, Britain (en_GB)
English, Canada (en_CA)
English, India (en_IN)
English, Ireland (en_IE)
English, New Zealand (en_NZ)
English, Singapore(en_SG)
English, South Africa (en_ZA)
English, US (en_US)
Finnish, Finland (fi_FI)
French, Belgium (fr_BE)
French, Canada (fr_CA)
French, France (fr_FR)
French, Switzerland (fr_CH)
German, Austria (de_AT)
German, Germany (de_DE)
German, Liechtenstein (de_LI)
German, Switzerland (de_CH)
Greek, Greece (el_GR)
Hebrew, Israel (he_IL)
Hindi, India (hi_IN)
Hungarian, Hungary (hu_HU)
Indonesian, Indonesia (id_ID)
Italian, Italy (it_IT)
Italian, Switzerland (it_CH)
Japanese (ja_JP)
Korean (ko_KR)
Latvian, Latvia (lv_LV)
Lithuanian, Lithuania (lt_LT)
Norwegian bokmål, Norway (nb_NO)
Polish (pl_PL)
Portuguese, Brazil (pt_BR)
Portuguese, Portugal (pt_PT)
Romanian, Romania (ro_RO)
Russian (ru_RU)
Serbian (sr_RS)
Slovak, Slovakia (sk_SK)
Slovenian, Slovenia (sl_SI)
Spanish (es_ES)
Spanish, US (es_US)
Swedish, Sweden (sv_SE)
Tagalog, Philippines (tl_PH)
Thai, Thailand (th_TH)
Turkish, Turkey (tr_TR)
Ukrainian, Ukraine (uk_UA)
Vietnamese, Vietnam (vi_VN)

SOURCE: http://us.dinodirect.com/Forum/Latest-Posts-5/Android-Versions-and-their-Locales-1-86587/

I think the best way is to run a sample code to find the supported locales. I've made a code snippet that does it:

final Locale[] availableLocales=Locale.getAvailableLocales();
for(final Locale locale : availableLocales)
  Log.d("Applog",":"+locale.getDisplayName()+":"+locale.getLanguage()+":"
    +locale.getCountry()+":values-"+locale.toString().replace("_","-r"));

the columns are : displayName (how it looks to the user), the locale, the variant, and the folder that the developer is supposed to put the strings into.

Here's a table I've made out of the 5.0.1 emulator: https://docs.google.com/spreadsheets/d/1Hx1CTPT82qFSbzuWiU1nyGROCNM6HKssKCPhxinvdww/

Weird thing is that for some cases, I got "#" which is something I've never seen before. It's probably quite new, and the rule I've chosen is probably incorrect for those cases (though it still compiles fine when I put such folders and files), but for the rest it should be fine.

If anyone knows about what the "#" is, and how to handle it, please let me know.

http://developer.android.com/reference/java/util/Locale.html

See CLDR for specific language support.

Ex : CLDR 1.8 for 2.3

http://cldr.unicode.org/index/downloads/cldr-1-8

Languages:

Afar [Qafar];
Afrikaans;
Akan;
Albanian [shqipe];
Amharic [አማርኛ];
Arabic [‎العربية‎];
Armenian [Հայերէն];
Assamese [অসমীয়া];
Asu [Kipare];
Atsam [cch];
Azerbaijani (Arabic) [azərbaycanca (ərəb)];
Azerbaijani (Cyrillic) [Азәрбајҹан (kiril)];
Azerbaijani (Latin) [azərbaycanca (latın)];
Bambara [bamanakan];
Basque [euskara];
Belarusian [беларуская];
Bemba [Ichibemba];
Bena [Hibena];
Bengali [বাংলা];
Blin [ብሊን];
Bosnian [Bosanski];
Breton [br];
Bulgarian [български];
Burmese [ဗမာ];
Catalan [català];
Central Morocco Tamazight (Latin) [Tamaziɣt (Latn)];
Cherokee [ᏣᎳᎩ];
Chiga [Rukiga];
Colognian [ksh];
Cornish [kernewek];
Croatian [hrvatski];
Czech [čeština];
Danish [dansk];
Divehi [‎ދިވެހިބަސް‎];
Dutch [Nederlands];
Dzongkha [རྫོང་ཁ];
Embu [Kĩembu];
English (Deseret) [𐐀𐑍𐑊𐐮𐑇 (𐐔𐐯𐑆𐐲𐑉𐐯𐐻)];
English (Shavian);
Esperanto;
Estonian [eesti];
Ewe [Eʋegbe];
Faroese [føroyskt];
Filipino;
Finnish [suomi];
French [français];
Friulian [furlan];
Fulah [Pulaar];
Ga [gaa];
Galician [galego];
Ganda [Luganda];
Geez [ግዕዝኛ];
Georgian [ქართული];
German [Deutsch];
Greek [Ελληνικά];
Gujarati [ગુજરાતી];
Gusii [Ekegusii];
Hausa (Arabic) [Hausa (Arab)];
Hausa (Latin) [Hausa (Latn)];
Hawaiian [ʻōlelo Hawaiʻi];
Hebrew [‎עברית‎];
Hindi [हिन्दी];
Hungarian [magyar];
Icelandic [íslenska];
Igbo;
Indonesian [Bahasa Indonesia];
Interlingua;
Inuktitut [ᐃᓄᒃᑎᑐᑦ ᑎᑎᕋᐅᓯᖅ];
Irish [Gaeilge];
Italian [italiano];
Japanese [日本語];
Jju [kaj];
Kabuverdianu;
Kabyle [Taqbaylit];
Kalaallisut;
Kalenjin;
Kamba [Kikamba];
Kannada [ಕನ್ನಡ];
Kazakh (Cyrillic) [Қазақ (Cyrl)];
Khmer [ភាសាខ្មែរ];
Kikuyu [Gikuyu];
Kinyarwanda;
Kirghiz [Кыргыз];
Konkani [कोंकणी];
Korean [한국어];
Koro [kfo];
Koyra Chiini [Koyra ciini];
Koyraboro Senni;
Kpelle [kpe];
Kurdish (Arabic) [‎كوردی (عەرەبی)‎];
Kurdish (Latin) [‎kurdî (لاتین)‎];
Langi [Kɨlaangi];
Lao [ລາວ];
Latvian [latviešu];
Lingala [lingála];
Lithuanian [lietuvių];
Low German [Plattdüütsch];
Luo [Dholuo];
Luyia [Luluhia];
Macedonian [македонски];
Machame [Kimachame];
Makonde [Chimakonde];
Malagasy;
Malay [Bahasa Melayu];
Malayalam [മലയാളം];
Maltese [Malti];
Manx [Gaelg];
Maori [mi];
Marathi [मराठी];
Masai [Maa];
Meru [Kĩmĩrũ];
Mongolian (Cyrillic) [монгол (Cyrl)];
Mongolian (Mongolian) [монгол (Mong)];
Morisyen [kreol morisien];
Nama [Khoekhoegowab];
Nepali [नेपाली];
North Ndebele [isiNdebele];
Northern Sami [davvisámegiella];
Northern Sotho [Sesotho sa Leboa];
Norwegian [norsk];
Norwegian Bokmål [norsk bokmål];
Norwegian Nynorsk [nynorsk];
Nyanja [ny];
Nyankole [Runyankore];
Occitan;
Oriya [ଓଡ଼ିଆ];
Oromo [Oromoo];
Pashto [‎پښتو‎];
Persian [‎فارسی‎];
Polish [polski];
Portuguese [português];
Punjabi (Arabic) [‎پنجاب (العربية)‎];
Punjabi (Gurmukhi) [ਪੰਜਾਬੀ (ਗੁਰਮੁਖੀ)];
Romanian [română];
Romansh [rumantsch];
Rombo [Kihorombo];
Russian [русский];
Rwa [Kiruwa];
Saho [ssy];
Samburu [Kisampur];
Sango [Sängö];
Sanskrit [संस्कृत भाषा];
Sena;
Serbian (Cyrillic) [Српски (Ћирилица)];
Serbian (Latin) [Srpski (Latinica)];
Shambala [Kishambaa];
Shona [chiShona];
Sichuan Yi [ꆈꌠꉙ];
Sidamo [Sidaamu Afo];
Simplified Chinese [中文（简体）];
Sinhala [සිංහල];
Slovak [slovenčina];
Slovenian [slovenščina];
Soga [Olusoga];
Somali [Soomaali];
South Ndebele [isiNdebele];
Southern Sotho [Sesotho];
Spanish [español];
Swahili [Kenya];
Swati [Siswati];
Swedish [svenska];
Swiss German [Schwiizertüütsch];
Syriac [‎ܣܘܪܝܝܐ‎];
Tachelhit (Latin) [tamazight (Latn)];
Tachelhit (Tifinagh) [ⵜⴰⵎⴰⵣⵉⵖⵜ (Tfng)];
Tagalog;
Taita [Kitaita];
Tajik (Cyrillic) [tg (Cyrl)];
Tamil [தமிழ்];
Taroko [trv];
Tatar [Татар];
Telugu [తెలుగు];
Teso [Kiteso];
Thai [ไทย];
Tibetan [པོད་སྐད་];
Tigre [ትግረ];
Tigrinya [ትግርኛ];
Tonga [lea fakatonga];
Traditional Chinese [繁體中文];
Tsonga [Xitsonga];
Tswana [Setswana];
Turkish [Türkçe];
Tyap [kcg];
Uighur (Arabic) [ug (Arab)];
Ukrainian [українська];
Urdu [‎اردو‎];
Uzbek (Arabic) [‎اۉزبېک (Араб)‎];
Uzbek (Cyrillic) [Ўзбек (Кирил)];
Uzbek (Latin) [o'zbekcha (Lotin)];
Venda [Tshivenḓa];
Vietnamese [Tiếng Việt];
Vunjo [Kyivunjo];
Walamo [ወላይታቱ];
Welsh [Cymraeg];
Wolof (Latin) [wo (Latn)];
Xhosa [isiXhosa];
Yoruba [Èdè Yorùbá];
Zulu [isiZulu]

Locale IDs can be found in:

http://www.localeplanet.com/icu/

Steps to follow

Step 1 : Need to find which all Languages supported on Android

Sol - follow my above answer ie in cldr-1-8 Languages.

Step 2 : Since cldr-1-8 Languages does not give u Locale short form which is need to be found for desire language Sol - Once language is available in cldr-1-8 Languages list then check for the shortform in http://www.localeplanet.com/icu/ link

Example :For language Hindi [हिन्दी] (1)we need to search its present in cldr-1-8 language then (2)search for Hindi in http://www.localeplanet.com/icu/ for Locale id its comes out to be http://www.localeplanet.com/icu/hi/index.html this link and see Locale id from it .