Rostojávri (also Rostujavri, Swedish Råstojaure ) is a lake on the border between Norway and Sweden, 680 meters above sea level. The Norwegian share ( 3.67 km ²) is located on the territory of the commune Målselv in Fylke Troms, the much larger Swedish ( 30.57 km ²) in the municipality of Kiruna, Norrbotten County in the historical province of Lapland.

The Norwegian Rostojávri bordered on the south side of the Øvre Dividal National Park. The lake is next to other fishable on Arctic char and grayling. In the roadless area, there are reindeer herding.

The lake was first mentioned in 1559 as Råsta TRESK. Today's notation consists of the non- deductible prefix Rosto, which also occurs in other names through the mountains, and the North Amish jávri for sea together.

The lake has two outlets and thus forms a Seebifurkation. Approximately 55 % of the water flows to the northwest (Norway ) in the Råstaelva, an indirect tributary of the Målselva, and finally into the Norwegian Sea. The rest flows to the southeast (Sweden) on Råstätno in the Lainioälven, a tributary of the Torne River, and finally into the Bothnian Bay.