Sør-Trøndelag (lit. transl. South Trøndelag; Southern Sami: Åarjel-Tröndelaage) is one of the 19 multi-member constituencies of the Storting, the national legislature of Norway. The constituency was established in 1921 following the introduction of proportional representation for elections to the Storting. It consists of the municipalities of Åfjord, Frøya, Heim, Hitra, Holtålen, Indre Fosen, Malvik, Melhus, Midtre Gauldal, Oppdal, Orkland, Ørland, Osen, Rennebu, Rindal, Røros, Selbu, Skaun, Trondheim and Tydal in the county of Trøndelag. The constituency currently elects nine of the 169 members of the Storting using the open party-list proportional representation electoral system. At the 2021 parliamentary election it had 247,553 registered electors.