Alcobaça is a Portuguese city and municipality in the intermunicipal community Oeste and the region Oeste e Vale do Tejo, in the historical province of Estremadura, and in the Leiria District. The city grew along the valleys of the rivers Alcoa and Baça, from which it derives its name. The municipality population in 2011 was 56,693, in an area of 408.14 square kilometres (157.58 sq mi). The city proper has a population of 15,800 inhabitants.