Boknafjord, also referred to as Boknafjorden, is a large fjord in Rogaland county, Norway. It lies between the cities of Stavanger and Haugesund and forms a dominant geographic feature of the central part of the county. The main body of the fjord is shared by the municipalities of Kvitsøy, Stavanger, Tysvær, Bokn, and Karmøy, and numerous smaller fjords branch off from it, reaching most other municipalities in the region.
Geographically, Boknafjord extends up to approximately 96 kilometres (60 mi) inland, terminating at the innermost point of the Hylsfjorden. Notable subsidiary fjords include the Saudafjorden, Sandsfjorden, Vindafjorden, Hervikfjorden, Førresfjorden, Erfjorden, Jøsenfjorden, Årdalsfjorden, Idsefjorden, Høgsfjorden, Lysefjorden, and Gandsfjorden. The fjord’s breadth accommodates many islands, among which the larger and more significant are Vestre Bokn, Kvitsøy, Rennesøy, Ombo, Finnøy, Mosterøy, and the Sjernarøyane archipelago.
A major infrastructure project associated with the fjord is the Rogfast subsea tunnel. This 24‑kilometre (15‑mi) road tunnel, extending to a depth of 350 metres (1,150 ft) beneath the Boknafjord and the neighboring Kvitsøyfjord, aims to provide a ferry‑free highway connection between Stavanger and Haugesund. Construction began in 2018, with an anticipated completion date in 2029; upon completion, it is expected to be the longest and deepest underwater road tunnel worldwide. Initial cost estimates of €500–600 million have since been revised upward to approximately €1.7 billion.