Karl Åke Seyffarth (15 December 1919 – 1 January 1998) was a Swedish speed skater who specialised in long distance events. He set new world records on the 5,000 m (8:13.7) in 1941 and on the 3000 m (4:45.7) in 1942. He became European Allround Champions in 1947, winning both the 5,000 m and the 10000 m on his way to becoming European Champion. In addition to speed skating, Seyffarth also was one of Sweden's leading cyclists, but this career was hampered by an injury in a dirt biking accident in 1943.

Seyffarth participated in the 1948 Winter Olympics in St. Moritz, the first Winter Olympic Games to be held in twelve years. As a result of the lack of competition during, and shortly after, World War II, Seyffarth entered the 5,000 m as the world record holder, a record he had set almost exactly seven years earlier, in 1941. During his heat, Seyffarth seemed to be winning until a photographer tried to take a picture of him and stepped onto the ice. Seyffarth brushed the photographer, losing several seconds, and went on to lose his heat and finally come in seventh overall. The winner of the race was Reidar Liaklev with a time of 8:29.4, well above Seyffarth's 1941 world record of 8:13.7. Seyffarth's official 5,000 m time was 8:37.9.

The day after his disappointing 5000 m race, Seyffarth won Olympic silver on the 1,500 m, half a second behind Norwegian skater Sverre Farstad. The day after that, Seyffarth won Olympic gold on the 10000 m with a time of 17:26.30, not a particularly fast time considering that the world record at the time was 17:01.50. He won with relative ease, however, almost ten seconds ahead of silver medallist Lassi Parkkinen from Finland.