Ole Martin Ellefsæter (born 15 February 1939) is a retired athlete from Norway. He mostly competed in cross-country skiing, and won two gold medals at the 1968 Winter Olympics. At the 1966 FIS Nordic World Ski Championships he won one gold (4×10 km) and one silver (15 km) medal, and in 1971 he became the first Norwegian to win Vasaloppet. Anders Aukland and Jørgen Aukland are the only other Norwegians to win this ski race. Earlier in 1967, Ellefsæter won the 50 km event at the Holmenkollen ski festival, the same year he was awarded the Holmenkollen medal, shared with Toini Gustafsson.
Besides skiing Ellefsæter competed in the 3000 m steeplechase, winning the national title in 1960–1965. His personal best of 8:43.8 minutes was a world-top level results at that time and placed him 26th on the Norwegian all-time list. Ellefsæter competed at the 1962 European Championships, but failed to reach the final. For his accomplishments in both sports he received the Egebergs Ærespris in 1965. Later his statue was installed in Brumunddal where he grew up.
Ellefsæther worked for several years as a lumberjack, and later studied to become a forestry technician. He received the nickname "Uteligger" ("Homeless") after one skiing accident, where after a long training he was taken by surprise by the darkness, and had to stay overnight in the forest.
Ellefsæther was a popular singer. His 1966 single "Huldreslåtten" sold more than 25,000 copies in Norway. After the 1968 Olympics he had another hit "Alle kluter til", which was dedicated to the success of Norwegian team. He produced two more records, "Viser og gamle takter" (1967) and "I godt lag" (1969), the text for which was written by his neighbor Guttorm P. Haugen.