Time Prison is an unseen location mentioned in the episode "A Rickle in Time". Shleemypants threatens to imprison Rick, Morty, and Summer for illegally obtaining a Time Crystal.

Only knowledge about Time Prison comes from one quote by Shleemypants: "You know what they do to third-dimensional life forms in Time Prison? Same thing they do in every other prison, only forever." Based on that quote, it is presumed, that in Time Prison, time moves differently than in the normal reality so let it's inhabitants live forever.