Austfjorden is a fjord in Vestland county, Norway.

The village of Knarrviki and the Mongstad industrial area lie on the western shore of the Austfjorden.

The first of these is the 2-kilometre (1 mi) long Mjangersvågen with the small village of Mjanger the head of the bay.

At the Kjekallevågen bay, the Austefjorden stretches 6 kilometres (4 mi) farther southeast and the Hidnesfjorden branches off to the west and heads south for about 8 kilometres (5.0 mi).

At the head of the Hidnesfjorden, there is a 1.7-kilometre (1.1 mi) wide isthmus of land that separates this fjord from the Osterfjorden to the south.