Sigtuna is a locality situated in Sigtuna Municipality, Stockholm County, Sweden with 8,444 inhabitants in 2010. It is the namesake of the municipality even though the seat is in Märsta.Sigtuna is, despite its small population, for historical reasons often still referred to as a town. Statistics Sweden, however, only counts localities with more than 10,000 inhabitants as cities.Although less significant today, Sigtuna has an important place in Sweden's early history.