Karasjohka

 or is a river in Troms og Finnmark county, Norway. The long river runs through Kautokeino Municipality and Karasjok Municipality. The river is one of the most important rivers that drains the Finnmarksvidda plateau. It flows into the famous salmon-fishing Tana River near the Finnish village of Karigasniemi on the Norway-Finland border.
The river begins at the small Norwegian lake of Nuorttit Rávdojávri which lies inside the Øvre Anárjohka National Park, just inside the border with Finland. The river begins high on the Finnmarksvidda plateau and then flows north through Kautokeino and Karasjok municipalities. About west of the village of Karasjok, the river turns and heads to the east. At its confluence with the river Anarjohka, the two rivers form the Tana River. The Karasjohka river drains a watershed of . The European route E06 highway runs along the northern shore of the last of the river.