Grytøya seen from Hinnøya
|Area||108 km2 (42 sq mi)|
|Length||17 km (10.6 mi)|
|Width||10 km (6 mi)|
|Coastline||62 km (38.5 mi)|
|Highest elevation||1,012 m (3,320 ft)|
|Pop. density||4 /km2 (10 /sq mi)|
Grytøya (Norwegian) or Rivttek (Northern Sami) is an island in Harstad Municipality in Troms county, Norway. The 108-square-kilometre (42 sq mi) island lies just north of the large island of Hinnøya and south of the island of Bjarkøya. It is surrounded by the Vågsfjorden in the east and the Andfjorden in the west. The highest peak on the island is the 1,012-metre (3,320 ft) tall mountain Nona. The population of Grytøya (2017) is 433. The southeastern part of the island is the most agriculturally productive. 
The northern part of the island was formerly part of the old municipality of Bjarkøy, which merged with Harstad Municipality on 1 January 2013.
There is a ferry connection from Bjørnå (on Grytøya) to Vika (on the neighboring island of Hinnøya), just north of the town of Harstad. The main road on the island follows the coastline from the northeast at Fenes to Grotavær in the northwest. There is very little settlement on the northern coast, and no road connections there.
There used to be ferry connections to the neighboring islands of Bjarkøya and Sandsøya, but the Bjarkøy Fixed Link project created a bridge and undersea tunnel system connecting the three islands. They will open in late 2018.