Østby IL, founded in 1919, organises events such as the Trysil Ski Marathon.
Østby IL is best known as the organiser of the Østby ski relay race, which was held 40 times between 1935 and 1979. The Østby race was the biggest, most prestigious relay race of its time for ski clubs. Nearly every elite skier from Norway and Sweden competed.
In recent years, Østby IL has had great success organising the Trysil Ski Marathon, a seeding race for Vasaloppet and Birken which in 2007 drew nearly 300 entrants to the starting line. In terms of number of active-class athletes, the Trysil Ski Marathon is the largest annual sports event in Trysil.