Märsta (; roughly pronounced ) is a suburb of Metropolitan Stockholm, a locality and the seat of Sigtuna Municipality, Stockholm County, Sweden with 24,068 inhabitants in 2010. The town is situated close to Stockholm's main international airport, Arlanda. Even if its origins go back to around 500 AD Märsta is a wide spread modern residential area. Märsta has a mix of multi-storey dwellings and smaller houses. It is in a phase of expansion and new residential areas are built both in central parts of Märsta and in the surrounding areas like for instance Steningehöjden. Märsta can be reached by commuter trains from Stockholm running at quarterly intervals during daytime and by bus from Stockholm Arlanda Airport. The central parts of Märsta has a shopping area "Märsta Centrum" with various shops, pub and restaurants. Another smaller shopping area is "Valsta Centrum". East of the central parts of Märsta there is an industrial area and a bit further east close to the airport a shopping mall "Eurostop". Most parts of Märsta and the municipality of Sigtuna can be reached with local bus services originating at the railway station and also connecting with commuter trains.
The area has been populated since the stone age and due to the location of traditional Viking-land has rich archaeological remains from the Bronze Age, Iron Age and Viking age. There are many runestones and older ruins of stone castles and walls in the Märsta area.
The area of today's modern Märsta consisted of big farms and small communities, that were (and still are) typical for the landscape of the province Uppland. Märsta was just one of these farms but due to the location and importance of travelling between Stockholm and Uppsala, the farm had to turn into an inn. The important travelling road can be traced back to the Viking age and even older ages.
During the days of the Swedish Empire many of the old nobles became land owners in the area and built palaces like Steninge, Skånelaholm, Rosersberg and Venngarn. Even Sweden's oldest public school is located in Husby-Ärlinghundra, the parish of Märsta. It was built in 1697 and is today a museum.
The first telegraph pole in Sweden was placed in Märsta 1853 and the train station got built in the 1860s. It is currently the northern termini of the commuter railways in Stockholm, and a minor interchange to SJ. The name Märsta got along only because it was common for travellers even though they were placed on neighbouring farms.
The Märsta municipality was formed in 1952 due to a fusion of the parishes of Husby-Ärlinghundra, Norrsunda, Odensala and Skånela. In 1967 the parishes of Vidbo, Lunda and Skepptuna also merged into the municipality. In 1971 the cities of Sigtuna and Märsta were forged together and formed Sigtuna Municipality with Märsta as the seat of the ruling council.
In 1957 the Swedish government decided to build Stockholms new international airport, Stockholm Arlanda, at Halmsjön east of Märsta. In its decision the government mentioned the building of a town where the employees at the new airport could live. The town was located to Märsta. A plan for the residential area was made in 1960 and during the 1960:s the population of Märsta was almost four times doubled. A large part of the buildings in Märsta was built in the 1960:s. Expansion of Märsta to the east is restricted due to the 55 dB(A) noise area restrictions in force. There are not many older houses in the central parts of Märsta but south of Märsta you find Steninge Castle with an environment dating back to 1690. Steninge Castle is a popular tourist attraction.