The siege of Halicarnassus was fought between Alexander the Great and the Achaemenid Persian Empire in 334 BC. Alexander, who had no navy, was constantly being threatened by the Persian navy. It continuously attempted to provoke an engagement with Alexander, who would not oblige them. Eventually, the Persian fleet sailed to Halicarnassus, in order to establish a new defense. Ada of Caria, the former queen of Halicarnassus, had been driven from her throne by her younger brother Pixodarus of Caria. When Pixodarus died, Persian King Darius had appointed Orontobates satrap of Caria, which included Halicarnassus in its jurisdiction. On the arrival of Alexander in 334 BC, Ada, who was in possession of the fortress of Alinda, surrendered the fortress to him.

Halicarnassus was an ancient Greek city in Caria, in Anatolia. It was located in southwest Caria, on an advantageous site on the Gulf of Gökova, which is now in Bodrum, Turkey. The city was famous for the Mausoleum of Halicarnassus, also known simply as the Tomb of Mausolus, whose name provided the origin of the word "mausoleum". The mausoleum, built from 353 to 350 BC, ranked as one of the seven wonders of the ancient world.