Diocletian's Palace is a building in Split, Croatia, that was built by the Roman emperor Diocletian at the turn of the fourth century AD. Diocletian built the massive palace in preparation for his retirement on 1 May 305 AD. It lies in a bay on the south side of a short peninsula running out from the Dalmatian coast, four miles from Salona, the capital of the Roman province of Dalmatia.

Diocletian's Palace is an ancient palace built for the Roman emperor Diocletian at the end of the third century AD, which today forms about half of the old town of Split, Croatia. While it is referred to as a "palace" because of its intended use as the retirement residence of Diocletian, the term can be misleading as the structure is massive and more resembles a large fortress: about half of it was for Diocletian's personal use, and the rest housed the military garrison.