Sognsvann (or Sognsvannet[1]) is a 3.3 km circumference lake just north of Oslo, Norway.

Lying just within the greenbelt around Oslo, the lake is a popular recreational area, used as a camping, picnicking and bathing destination for the residents of Oslo during the summer, as well as a cross-country skiing, skating and ice fishing destination in the winter.

Part of the lake's popularity stems from its easy access from Oslo; Sognsvann station, located on the south end of the lake, is the final stop on line 5 on the Oslo Metro.

Svartkulp ("The black pool"), a small forest lake which is one of three nudist beaches in Oslo, lies a few hundred meters to the east of Sognsvann.

A pyramid marking the geographical center of Oslo municipality and county is installed on the east side of it, alongside Ankerveien.