Who Owns the Publishing Rights of my Ph.D. Thesis?

Did you sign an agreement to transfer copyright to someone else?

Does your university policy (example) or employment contract specify that someone else holds the copyright to your thesis?

If the answer to both questions is "no" then you, as the author of the thesis, hold the copyright.

In the US, most university students retain the copyright for their thesis. Often they are required to grant the university and/or ProQuest a non-exclusive license to distribute the thesis, but without giving up copyright.

You do, until you sign the rights away. This is regardless of whether you have a copyright page, thanks to the Berne Convention.

Note that depositing it in the library does not waive any of your rights.

You do transfer some rights when you deposit it through ProQuest but 1) you didn't mention doing so, 2) the form you would have signed if you had done so would have made what rights they wanted explicit, and 3) ProQuest does not request exclusive rights to publish and distribute your dissertation in any case , so you can publish parts or all of it in other venues without their permission.

Note that some publishers are hesitant to publish monographs based on dissertations accessible on ProQuest but this is a business decision not legal one. They fear the availability of the ProQuest version is a market threat that draws away from the salability of a monograph based on the dissertation. As a result, some students have asked ProQuest to embargo the dissertation for a few years, which is something ProQuest is happy to do.