Musdal Opp is a road uphill race in Tretten, Innlandet, Norway, climbing from Tretten station to Musdalseter hyttegrend. The route is just under 9 km, with 706 meters of elevation gain, making it a short mountain run focused on ascending the valley road efficiently. It is held each October and includes both a timed competition class and a recreational class without timing.
The race originated as a small test with 10 invited runners before expanding to a local event with over 100 participants. Mads Buhaug initiated the race, and past participants include runners from Lillehammer IF and Kåbbåi Racing Team, with Petter Johansen among the winners. The untimed recreational class was introduced after the race had grown, received positive feedback, and allows hikers or casual runners to participate without focusing on their time.