Mjåvatnet is a lake that lies in the municipality of Vefsn in Nordland county, Norway. The long, skinny, 2.61-square-kilometre (1.01 sq mi) lake lies between the lakes Ømmervatnet and Fustvatnet, about 15 kilometres (9.3 mi) northeast of the town of Mosjøen. The European route E6 highway passes along the west coast of the lake.

• List of lakes in Norway
• Geography of Norway