Hjalmar Johan "Hjallis" Andersen (born March 12, 1923) is a Norwegian speed skater who won three gold medals at the 1952 Winter Olympic Games in Oslo, Norway.

He was born on Rødøy, an island off the coast of Nordland in Norway. He grew up on Lademoen, a part of Trondheim where mostly workers lived, and where sport and friendship was an important part of life.

He made his international debut during the 1948 Olympic Games in St. Moritz, Switzerland 1948. He won the qualifying race for 1500 m, but he was still not selected for the Norwegian team for this distance. He was selected for the 10000 m team, but because of the terrible ice conditions he did not finish the race.

He was the best skater of the world in the period of 1950-1952. He was 3 times World Champion and 3 times European Champion in this period, in addition to winning 3 gold medals at the 1952 Olympic Games in Oslo (1500 m, 5000 m and 10000 m).

He quit skating after the 1952 Olympics, but he was talked into a new try in 1954. He won both the 5000 m and 10000 m at the European Championships in Davos, Switzerland this year, and he was second in the total standings. He qualified for the 1956 Olympics and earned a 6th place in the 10000 m.

During his career he set 5 World Records. His 10000 m World Record in 1949 (16.57,4) was the first official World Record below 17 minutes on the distance.

He was also a great cyclist at a national level, and in 1951 he was awarded "Egebergs Ærespris" (Honorary Price of Egeberg) for his achievements in speed skating and cycling.