Halicarnassus (Ἁλικαρνᾱσσός or Ἀλικαρνασσός Alikarnassós; Halikarnas) was an ancient Greek city at the site of modern Bodrum in Turkey. It was located in southwest Caria on a picturesque, advantageous site on the Ceramic Gulf. The city was famous for the tomb of Mausolus, the origin of the word mausoleum, built between 353 BC and 350 BC, and one of the seven wonders of the ancient world. It was part of the Persian Empire until captured by Alexander the Great at the siege of Halicarnassus in 334 BC.

Halicarnassus originally occupied only a small island near to the shore called Zephyria, which was the original name of the settlement and the present site of the great Castle of St. Peter built by the Knights of Rhodes in 1404; but in course of time, the island united with the mainland and the city extended to incorporate Salmacis, an older town of the Leleges and Carians and site of the later citadel.