Jan Thomas Jenssen (born 1 April 1996) is a Norwegian cross-country skier.

He made his World Cup debut in December 2017 in Lillehammer, finishing 51st.

Two years later, he recorded his first placement among the top 30, finishing 8th in the Lenzerheide mass start of the 2019–20 Tour de Ski.

[1] He obtained his first World Cup win in November 2023 after missing three years of World Cup racing, winning the 20 kilometer freestyle mass start in Ruka, Finland.

[citation needed] All results are sourced from the International Ski Federation (FIS).