Alghero (Italian: [alˈɡɛːro]; Algherese: L'Alguer [lalˈɣe]; Sardinian: S'Alighera [saliˈɣɛɾa]; Sassarese: L'Aliera [laˈljɛːɾa]) is a city of about 45,000 inhabitants in the Italian province of Sassari in the north west of the island of Sardinia, next to the Mediterranean Sea. The city's name comes from Aleguerium, which is a mediaeval Latin word meaning "stagnation of algae" (Posidonia oceanica).

The population is noted for having retained the language of the Crown of Aragon rulers from the end of the Middle Ages, when Sardinia was part of the Crown of Aragon; hence, Algherese (the Catalan dialect spoken there) is officially recognized as a minority language.

Alghero is the third university center in the island, coming after Cagliari and Sassari. It hosts the headquarters of the Università degli Studi di Sassari's Architecture and Design department.