Fossavatnsgangan is an annual ski marathon held in Ísafjörður, in the Westfjords of Iceland.

[3] The currently longest race over the distance of 50 km has only been held since 2004 and due to its challenges and difficulties has increasingly attracted international professional skiers, particularly Norwegians.

[3] In 2005 this 50 km marathon was added to the FIS, and that same year Fossavatn became a founding partner of the FIS Nordic Ski Marathon Cup, a series which includes the Holmenkollen Skimaraton in Norway, Tornedalsloppet in Sweden, Oulun Tervahiihto in Finland and the Fossavatn Ski Marathon in Iceland.

[3] The most successful athlete of the marathon since its inception in 1935 is a local skier named Kristján Rafn Guðmundsson, 12 times winner of the Fossavatn Ski Marathon in the 1960s and 1970s.

[3] The most prolific competitor is another local named Sigurður Jónsson who first competed in 1938.