The Roman Catholic Diocese of Willemstad (Latin: Dioecesis Gulielmopolitana; Dutch: Bisdom Willemstad; Papiamento: Diosesano (di Obispado) di Willemstad) is a diocese of the Latin Church of the Roman Catholic Church in the Caribbean.

The diocese encompasses the territory of the Kingdom of the Netherlands in the Caribbean: the countries (Dutch: landen) Aruba, Curaçao, Sint Maarten (the southern half of St. Martin) and the islands Bonaire, St. Eustatius, Saba (which are part of the Netherlands).

The diocese is a suffragan of the Archdiocese of Port of Spain, and a member of the Antilles Episcopal Conference.

It was elevated to an apostolic vicariate on 20 September 1842 and to the Diocese of Willemstad on 28 April 1958.

Some priests are members of the Society of the Divine Word (SVD), Order of Preachers (OP), Michaelites (CSMA), and Salesians of Don Bosco (SDB).