Rasmus Fossum Tiller, born on 28 July 1996, is a professional Norwegian cyclist with UCI ProTeam Uno-X Mobility.
In 2022, Tiller won the Norwegian National Road Championships ando claimed second place at the Binche–Chimay–Binche race. He demonstrated his consistency with sixth-place finishes in Omloop Het Nieuwsblad and Nokere Koerse, and rounded out the top ten in Le Samyn and Dwars door het Hageland.
The following year, 2023, saw Tiller winning Dwars door het Hageland and securing a stage win at the Tour of Britain. Tiller also finished second in both the Circuit Franco-Belge and Druivenkoers Overijse, took third at the Grand Prix du Morbihan, and placed in the top ten across several other significant races, including a fifth place at the National Road Championships, sixth at the UEC European Road Championships, seventh overall at the Deutschland Tour, and eighth at the Egmont Cycling Race.