How to assign an issue to non contributors?

Question

Is it possible to assign an issue to non-contributors on a project?

I have a project that others want to work on, but I'm the only one that can get assigned.

Answer 1

Update June 2019, three years later:

You could ask that non-contributor to... leave a comment on the issue.
Because then, you can Assign issues to issue commenters:

Now, when a user with read-only access to a repository comments on an issue, a maintainer of that repository can assign the issue to that user.

If the user does not want to be assigned to the issue, they may unassign themselves by clicking unassign me next to their name.

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Original answer Dec. 2016:

The official rule is:

You can only create assignments for yourself, collaborators on personal projects, or members of your organization with read permissions on the repository.

So if you can add other users as collaborators to your repo, you will be able to assign to them issues.