Osterfjorden is one of three fjords surrounding the island Osterøy.
The fiord runs between Lindås and Osterøy and is 27 km long, 1-3 km wide. The largest depth is 639 m.
It connects Sørfjorden in the south to Veafjorden in the east. Along Osterfjorden are the villages of Knarvik, Hjellvik, Eikanger, Hosanger, Fotlandsvåg, Tysse and Stamnes