Ekerö Municipality (Ekerö kommun) is a municipality in Stockholm County in east central Sweden. The name comes from the island Ekerö, and literally means "Oak Island". Its seat is located in the town of Ekerö.
Ekerö is the only municipality in the Lake Mälaren region composed exclusively of islands. Land elevation has reduced the number of islands to 140, the largest of which, distinguished on the map below, are Adelsö, Munsö, Ekerö, Färingsö, and Lovö. 2000 years ago, during the Roman Iron Age, Färingsö was more of an archipelago of 20 islands.
Originally, when the first local government acts were implemented in Sweden in 1863, eight rural municipalities were created, each corresponding to an old parish. The municipal reform of 1952 grouped them in two new larger entities. The next reform in 1971 merged them into the present municipality.