The Foix (Catalan pronunciation: [ˈfoʃ]) is a river in Catalonia in the province of Barcelona, northeastern Spain. Its source is near La Llancuna in the Comarca of Anoia 800 m above the sea. Later it runs through the Comarca of Alt Penedès, where it feeds a reservoir in the nature reserve of Parc del Foix since 1928, which is highly important for the drinking water supply of the densely populated coastal plain between Barcelona and Tarragona. Then it goes through the Comarca of Garraf from north to the south where it ends into the Mediterranean Sea west of the village of Cubelles.