The siege of Silves was an action of the Third Crusade and the Portuguese Reconquista in 1189. The city of Silves in the Almohad Caliphate was besieged from 21 July until 3 September by the forces of Portugal and a group of crusaders from northern Europe on their way to the siege of Acre. The defenders capitulated on terms, the city was handed over to Portugal and the crusaders took a portion of the spoils.

The Almohad Caliphate launched a major offensive against the Kingdom of Portugal in the spring of 1190 that lasted into the summer of 1191. The Caliph Yaʿqūb al-Manṣūr crossed over from Africa to take personal command of his forces. The campaign of 1190 was underwhelming because of assistance Portugal received from passing armies of the Third Crusade. The sieges of Tomar, Santarém and Silves had to be abandoned, but the caliph overwintered in Seville. The campaign of 1191 reversed Portugal's recent reconquests, captured Silves after a second siege and pushed the frontier north to the Tagus.