The U20 SM-sarja ('Under-20 Finnish Championship Series') is the premier junior men's ice hockey league in Finland.

The league was founded by the Finnish Ice Hockey Association in 1945 and a Finnish Champion in men's under-20 ice hockey has been named annually since the league's inaugural season – with the exception of the 2019–20 season, in which the playoffs were cancelled due to the COVID-19 pandemic.

Most of the senior clubs of U20 teams play in the Liiga, the premier men's ice hockey league in Finland.

Notable exceptions include Jokerit, Kiekko-Espoo, Rovaniemen Kiekko (RoKi), and TUTO Hockey, all of which play in the second-tier Mestis.

The abbreviations ry and rf refer respectively to the Finnish and Swedish terms for a registered non-profit organization in Finland (Finnish: rekisteröity yhdistys; Swedish: registrerad förening).