Rostojávri

, , or is a lake on the border between Norway and Sweden. The Norwegian part of the lake (smaller) is located in Målselv Municipality in Troms county and the Swedish part of the lake (larger) is located in Kiruna Municipality in Norrbotten County. The Norwegian part of the lake lies inside Øvre Dividal National Park. The lake lies at an elevation of and covers a total area of ; with located in Norway and the remaining are located in Sweden.

==Hydrology== The lake straddles two watersheds. To the northwest it drains into the river Rostaelva, a tributary of the river Målselva, which runs into the Atlantic Ocean. To the southeast it drains into the Rostoeatnu, a source river of the Lainio River, itself a tributary of the Torne River, which drains into the Bothnian Bay of the Baltic Sea.