Sigtuna Municipality (Sigtuna kommun) is a municipality in Stockholm County in east central Sweden. Its seat is located in the town of Märsta, approximately 37 km north of the Swedish capital, Stockholm.
The municipality is a part of Metropolitan Stockholm.
The municipality consists of several former local government units and was formed in 1971. It got its name from the small, but very old, City of Sigtuna, but the seat was placed in the larger modern town of Märsta.
The three towns of the municipality are Märsta (pop. 23,000), Sigtuna (pop. 8,000) and Rosersberg (pop. 1,400), of which Märsta is the municipal seat and Sigtuna with its old and important history is a popular tourist destination.