Altra is an island in Alstahaug Municipality in Nordland county, Norway. The 0.24-square-kilometre (59-acre) island lies between the large island of Alsta and the small island of Tenna (in Herøy Municipality). The flat island is rather unusual in the area because it is about 12 kilometres (7.5 mi) long and at most about 2 kilometres (6,600 ft) wide at the northern end. Most of the island is very narrow, and in some places, it is only about 60 metres (200 ft) wide.

There are a few small villages on the island: Austbø in the north, Korsvegen and Blomsøya in the middle, and Hestøya in the south. The island has a regular ferry connection to the neighboring islands of Alsta and Sør-Herøy. In 2016, there were 76 residents living on the island.

• List of islands of Norway