Josephus’ narrative of Onias IV in Ant. 13.62-73 is an account of a Judean refugee who flees to Egypt and manages to acquire land in both Alexandria and Heliopolis. He is also given the authority to construct a temple on his Heliopolis property, which Josephus describes to have previously been δέσποτος. This is a technical term used in the papyri and by classical authors to designate ownerless property, which could be acquired legally only by purchase at the public auction and, in the Roman period, also directly from the idios logos. Scholars have long endeavoured to reconstruct the history behind Josephus’ narrative of the temple of Onias, but they have yet to investigate the function of this technical term within the larger narrative of Ant. 13.62-73, nor the insights that it might provide regarding the historicity of the account. The present article enters into the world of Ptolemaic land tenure in order to contextualize Josephus’ account of Onias’ acquisition of an ownerless temple. It demonstrates that Josephus’ story of Onias’ temple is more nuanced than previously thought.