Sundvatnet (Northern Sami: Sopmirjávri) is a lake in Deatnu-Tana Municipality in Finnmark county, Norway. The 5.54-square-kilometre (2.14 sq mi) lake lies about 5 kilometres (3.1 mi) northwest of the village of Rustefjelbma. The Tanafjorden lies less than 1 kilometre (0.62 mi) west of the lake.