Korssjøen is a lake in the municipality of Røros in Trøndelag county, Norway. The lake is located about 16 kilometres (9.9 mi) southeast of the town of Røros. The lake Rambergsjøen lies about 5 kilometres (3.1 mi) to the north and the lake Flensjøen lies about 10 kilometres (6.2 mi) to the east.

• List of lakes in Norway