Selfoss is a waterfall in the river Jökulsá á Fjöllum in the north of Iceland which drops over some waterfalls about 30 km before flowing into Öxarfjörður, a bay of the Arctic Sea.
A few hundred meters downstream of the Selfoss waterfall (11 metres (36 ft) high), the Dettifoss waterfall is situated, the most powerful waterfall of Europe. The river originates as melt water from the glacierVatnajökull and therefore the water flow varies depending on the season, the weather and volcanic activity. The river falls 44 metres (144 ft) over a width of 100 metres (330 ft). Below the falls, the river passes through a gorge which is part of the Jökulsárgljúfur National Park.