Gratangen is a municipality in Troms county, Norway. It is part of the Hålogaland traditional region. The administrative centre of the municipality is the village of Årstein. The municipality encompasses the land on both sides of the Gratangen fjord. European route E6 runs through the southeastern part of the municipality. The largest settlement in the municipality is Årstein, which is located approximately 60 km north of Narvik and 85 km east of Harstad.
The municipality of Gratangen was established on 1 July 1926 when it was separated from the municipality of Ibestad. The initial population of Gratangen was 1,967. The municipal boundaries have not changed since then.
The municipality is named after the Gratangen fjord (Old Norse: Grjótangr). The first element is grjót which means "stone" and the last element is angr which means "fjord".