Edy Sixten Jernberg (6 February 1929 – 14 July 2012) was a Swedish cross-country skier and one of the most successful cross-country skiers of all time. Between 1952 and 1964 he took part in 363 ski races, finishing within the podium in 263 and winning 134 of them; during this period he won four world titles and nine Olympic medals. In 12 starts over three consecutive Winter Games he never finished worse than fifth place, and between 1955 and 1960, he won 86 out of 161 competitions.
Jernberg was a blacksmith and a lumberjack before beginning his career as a cross-country skier. He specialized in the longer distances, with four of his eight gold medals coming over 50 km, one over 30 km and three in 4×10 km. He also won Vasaloppet twice, 1955 and 1960. He won the 15 km at the Holmenkollen ski festival in 1954.
At one competition, Jernberg had a fever and coughed up blood, but still finished the 50 km event. Gunde Svan said: "It was almost like [Sixten] didn't like his own body and tried to punish it in different ways."
For his cross-country skiing successes, Jernberg was awarded the Holmenkollen medal in 1960 (shared with Helmut Recknagel, Sverre Stensheim and Tormod Knutsen). He was also awarded the Svenska Dagbladet Gold Medal in 1956 (shared with pentathlete Lars Hall).
Jernberg retired after the Olympic Winter Games of 1964. In 1965, the International Olympic Committee awarded Jernberg the Mohammed Taher Trophy for his contributions to Nordic skiing. He died of cancer at the age of 83. He was survived by son Edy. His nephew Ingemar became an Olympic pole vaulter.