Mattias Skjelmose Jensen (born 26 September 2000) is a Danish professional cyclist who rides for UCI WorldTeam Lidl–Trek.

A promising youth rider, Skjelmose finished in top positions in junior categories of major races, and won the Tour du Pays de Vaud in 2018. Shortly after, he had a setback after receiving a ten-month suspension due to a doping test revealing traces of the performance-enhancing drugs originating from dietary supplements. He returned to racing in 2019, and initially joined UCI Continental team Leopard TOGT Pro Cycling before turning professional in 2021 with UCI WorldTeam Trek-Segafredo, after riding for the latter as a stagiare since 2020. He experienced a major breakthrough in 2023, finishing second behind Tadej Pogačar in La Flèche Wallonne, and winning the Tour de Suisse.