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.

Diocletian, nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.