The Battle of Diu was a battle that took place near Diu, India, between Portugal and a joint fleet of Egypt and the sultan of Gujarat February 3, 1509.

The Egyptian fleet, manned mostly by Turks, was sent by the Egyptian sultan to support the muslim ruler of Gujarat. The Portuguese had a force of 18 ships, commanded by the viceroy Francisco de Almeida. The battle was to avenge the defeat at the battle of Chaul (1508), where the viceroy's son was killed. The allied side had 100 ships, but only 12 were major vessels, the rest were small craft. The Portuguese ships had guns of greater caliber, better artillery crews, were better manned and better built. The Portuguese naval infantry also had advantage over the Turks, not only because they were better armed and equipped (armor, arquebuses and a type of grenade made of clay with gunpowder inside), but because in general Portuguese troops were seasoned professional seamen, mostly warrior nobility with an huge ascendancy over the Turks, not only in physical strength and size but in combat skills. The battle resulted in a major victory for the Portuguese, with all Egyptian and Gujarati ships being sunk or captured. Due to their overwhelming technical superiority, the Portuguese started the battle with a massive bombardment followed by hand-to-hand combat (boarding). The battle took place in the harbour of Diu, where the allied fleet was anchored. The Portuguese did not lose a single ship.

pl:Bitwa morska pod Diu