Our Lady Star of the Sea and St Winefride, Amlwch is a Roman Catholic church in Amlwch, a town on the island of Anglesey, north Wales. It was built in the 1930s to a design by an Italian architect, Giuseppe Rinvolucri, using reinforced concrete. The church is in the shape of an upturned boat, reflecting Amlwch's maritime heritage, and is dedicated to Our Lady, Star of the Sea (a title of St Mary) and St Winefride, a Welsh saint.
The church was closed between 2004 and 2011 because of structural problems that required costly repairs. The church is a Grade II* listed building, a designation given to "particularly important buildings of more than special interest", because it is a "remarkable inter-war church", built to "a highly unusual and experimental design". The Twentieth Century Society has called it "a rare and unique church", and it has also been called "one of Britain's most avant-garde churches".