Gullmarn, also known as Gullmarsfjorden or Gullmaren, is a threshold fjord in the middle of Bohuslän Archipelago on the west coast of Sweden. It is the largest of the Bohuslän fjords with a length of 25 km and a width ranging from 1–3 km. At its mouth, the depth is 45 m, plunging to 125 m at its greatest depth near Alsbäck. The name "Gullmarn" means "God's sea" and comes from Old Norse. At its northern end the fjord branches into the Färlev and Saltkälle fjords.
Its shoreline has steep rock walls marked by many valleys containing streams and rivers. Deeply cut ravines are typical and steep cliffs alternate with sandy beaches and meadows.The fjord was designated as Sweden's first marine conservation area in 1983. The nature reserve covers 16,499 ha and parts of several municipalities.
Coordinates 58°17'2.268" N 11°30'7.478" E