Gnesta is a bimunicipal locality and the seat of Gnesta Municipality, Södermanland County, Sweden with 5,562 inhabitants in 2010.
It is on the border to Stockholm County, and a minor part of Gnesta is in Södertälje Municipality. As situated near the county boundary Gnesta is served by Stockholm commuter rail which has a terminus here.
Gnesta is the location for the 2009 film adaptation of the Stieg Larsson book The Girl with the Dragon Tattoo, representing the fictional Hedestad and Hedeby Island.
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