Dettifoss is a waterfall in Vatnajökull National Park in Northeast Iceland, and is reputed to be the second most powerful waterfall in Europe after the Rhine Falls.[2] Dettifoss is situated on the Jökulsá á Fjöllum river, which flows from the Vatnajökull glacier and collects water from a large area in Northeast Iceland. The sediment-rich runoff colours the water a greyish white.

The falls are 100 metres (330 ft) wide and have a drop of 44 metres (144 ft) down to the canyon Jökulsárgljúfur.[3] It is the second largest waterfall in Iceland in terms of volume discharge (behind the Urriðafoss), having an average water flow of 193 m³/s. The superlative of "most powerful" comes from its water flow times its fall distance.