Selbusjø or Selbusjøen is the 17th largest lake in Norway. It is located in Sør-Trøndelag county, primarily in the municipality of Selbu, although the western end of it lies in Klæbu. The 58.26-square-kilometre (22.49 sq mi) lake is the largest lake in Sør-Trøndelag county. Selbusjø is part of the Nea-Nidelv watershed, with the Nea River flowing into it on the eastern end and the Nidelva River flowing out the western end.