The siege of Tripoli occurred in 1551 when the Ottoman Turks and Barbary pirates besieged and vanquished the Knights of Malta in the Red Castle of Tripoli, modern Libya. The Spanish had established an outpost in Tripoli in 1510, and Charles V remitted it to the Knights in 1530. The siege culminated in a six-day bombardment and the surrender of the city on 15 August.

The Invasion of Gozo took place in July 1551, and was accomplished by the Ottoman Empire against the island of Gozo, following an unsuccessful attempt to conquer nearby Malta on 18 July 1551. It was followed by a victorious campaign with the siege of Tripoli.