Fustvatnet is a lake that lies in the municipality of Vefsn in Nordland county, Norway. The 10.59-square-kilometre (4.09 sq mi) lake lies just south of the lake Mjåvatnet, about 5 kilometres (3.1 mi) northeast of the town of Mosjøen. The European route E6 highway follows the northwestern coastline.

• List of lakes in Norway
• Geography of Norway