The Battle of Gaza was a military conflict near Gaza in 312 BC at the end of the 4th century BC.

The battle was a military highlight of the Third War of the Diadochi. In this battle fought Demetrios Poliorketes, son of Antigonos Monophthalmos, who wanted to rule over Alexanders Empire as a whole against Seleukos and Ptolemy I, who wanted to rule over their share of the empire.

Among other Antigonus defeated the satrap of Babylon, Seleucus, who fled to Egypt to Ptolemy. The apparent superiority of Antigonus led the last independent Diadochi together into a unity of purpose against him. The initiative was started by Ptolemy, who felt directly threatened by Antigonus. He was joined by Cassander in Macedon, Lysimachus in Thrace and Asandros in Caria. Conversely, Antigonus was proclaimed as regentof the empire by the imperial army in opposition to Cassander, who was explained to the enemy of the Empire. He legitimised his claim in the name of King Alexander IV, who was in captivity Cassander's. In fact, he aspired the kingship himself in an undivided empire of Alexander. Opened in the spring of 314 BC Antigonus fought for the now third Diadochenkrieg and quickly gained posession of Syria, and Phoinikien Coelesyria under his control, until 313 BC he conquered successively Gaza and the Phoenician seaports like Sidon and Tyre.

Antigonus now turned his attention and the main parts of his army towards Asia Minor, to concentrate himself to the fight against Cassander and Lysimachus. He had appointed his son Demetrius Poliorcetes strategos of Syria with the mission to defend the front against Egypt. Ptolemy was not willing to accept the loss of the control of the so important seaports Phoinikiens and used the absence of Antigonus by 312 BC to start a counteroffensive.

Ptolemy launched an invasion of Syria. With 18,000 infantry and 4,000 cavalry he arrived to Gaza in early 312 BC.

Demetrius decided to offer him battle, but was routed; losing 500 men killed, a further 8,000 taken prisoner, and losing all his elephants. He retreated to Tripolis in Phoenicia.