She is the only Canadian Olympian to win five medals in a single Olympic games and the first female speed skater to win five medals in a single games at the 2006 Winter Olympics in Turin, Italy. She was a world record holder in the 3000 m until March 2019, when her time was beaten by Martina Sáblíková. She also holds the Canadian records over 1500 m and 5000 m. Klassen is the leader of the Adelskalender, which is the all-time world ranking for speed skating. In 2003, Klassen became the first Canadian in 27 years to win the overall title at the World Speed Skating Championships.