Gresvatnet or Grasvatnet (Southern Sami: Graesiejaevrie) is a lake on the border between Norway and Sweden. Most of the lake lies in the municipality of Hemnes in Nordland county (Norway) and then a small portion crosses the border into Storuman Municipality in Västerbotten county (Sweden). The lake lies about 25 kilometres (16 mi) east of the village of Korgen, and just a few kilometres northeast of the mountain Oksskolten and the Okstindbreen glacier.