How is ownership established over non-owned things? We suggest that people may view ownership as a kind of credit given to agents responsible for making possession of a non-owned object possible. On this view, judgments about the establishment of ownership depend on attributions of responsibility. We report three experiments showing that people's judgments about the establishment of ownership are influenced by an agent's intent and control in bringing about an outcome, factors that also affect attributions of responsibility. These findings demonstrate that people do not just consider who was first to possess an object in judging who owns it, and are broadly consistent with the view that ownership is acquired through labor. The findings also suggest that rather than exclusively being the product of social conventions, judgments about the establishment of ownership over non-owned things also depend on the psychological processes underlying the attribution of responsibility. (Contains 3 figures and 1 supplementary data.)