Värmdö Municipality is a municipality in Stockholm County in east central Sweden. Its seat is in the town of Gustavsberg, with a population of 9,682 (2005), on the main island at an elevation of 37 metres (121 ft).

Värmdö is an island in the innermost region of the Stockholm archipelago and covers an area of 181.40 km2, making it the largest island in the archipelago. Värmdö is after Gotland and Öland the third largest island on the eastern coast of Sweden.