Nagu is a former municipality and parish of Finland, located in the Southwest Finland region. It lies in the Archipelago Sea area of the country's southwestern coast.
On 1 January 2009, Nagu was consolidated with the municipalities of Houtskär, Iniö, Korpo and Pargas to form the new town of Väståboland. On 1 January 2012, the name Väståboland was changed to Pargas, so Nagu is today part of the town of Pargas.