Harald Maartmann’s father and uncle, Rolf and Erling, were footballers who represented Norway the 1912 Stockholm Olympics. Harald, however, was more interested in cross-country skiing and first gained attention in 1949, when he took silver in the 4x10 km relay at the national championships. His breakthrough year, however, was in 1950, when he won national titles in the 17 and 50 km events. This led to his selection for that year’s World Championships, where he was 7th in the 18 km and 5th in the 50 km. The following year he was third in the 50 km at the national championships and in 1952 he was selected to represent Norway at that year’s Winter Olympics in Oslo. There, he placed eighth in the 50 km event. By career, Maartmann was a forester.