Riddarfjärdssimningen is an open water swim in central Stockholm, with swimmers racing in Riddarfjärden by Norr Mälarstrand. The main individual distances are 1,609 meters and 3,200 meters, suiting swimmers who want a city swim longer than a pool race but still compact and easy to follow from shore.
The event is run by SK Neptun and Spårvägen together with Swimshop.se, drawing a wide field: young swimmers, masters, recreational entrants, and elite competitors share the same setting. It also hosts Swedish open water championship racing for senior, U21, youth, and masters categories, with relay formats such as 4 x 1,250 meters and mixed 4 x 1,250 meters adding more club-team action. The race has been held over forty times, and its mid-city location makes it unusually spectator-friendly for an open water swim.