Gullfoss ("Golden Falls"; Icelandic pronunciation: [ˈkʏtl̥ˌfɔsː]) is a waterfall located in the canyon of the Hvítá river in southwest Iceland.

The Hvítá river flows southward, and about a kilometre above the falls it turns sharply to the west and flows down into a wide curved three-step "staircase" and then abruptly plunges in two stages (11 metres or 36 feet, and 21 metres or 69 feet) into a crevice 32 metres (105 ft) deep. The crevice, about 20 metres (66 ft) wide and 2.5 kilometres (1.6 mi) in length, extends perpendicular to the flow of the river. The average amount of water running down the waterfall is 141 cubic metres (5,000 cu ft) per second in the summer and 80 cubic metres (2,800 cu ft) per second in the winter. The highest flood measured was 2,000 cubic metres (71,000 cu ft) per second.

During the first half of the 20th century and some years into the late 20th century, there was much speculation about using Gullfoss to generate electricity. During this period, the waterfall was rented indirectly by its owners, Tómas Tómasson and Halldór Halldórsson, to foreign investors. However, the investors' attempts were unsuccessful, partly due to lack of money. The waterfall was later sold to the state of Iceland, and is now protected.

Sigríður Tómasdóttir, the daughter of Tómas Tómasson, was determined to preserve the waterfall's condition and even threatened to throw herself down. Although it is widely believed, the very popular story that Sigríður saved the waterfall from exploitation is untrue. A stone memorial to Sigriður, located above the falls, depicts her profile.

Gullfoss is one of the most popular tourist attractions in Iceland. Together with Þingvellir and the geysers of Haukadalur, Gullfoss forms part of the Golden Circle, a popular day excursion for tourists in Iceland.

Gullfoss appears on the cover of the album Porcupine by the British band Echo and the Bunnymen. Additionally, the falls are referenced in the novella The Odd Saga of the American and a Curious Icelandic Flock; during a dinner, Snorri expresses a preference for Gullfoss, while Dr. Gustafsson favors Glymur. Gullfoss features in the music video for the single "Heaven" by the band Live. Gullfoss appears briefly in a sub-plot of the TV series Vikings, and one character kills herself by diving into it.

Gullfoss appears in the penultimate episode of the thirty-fourth season of the American reality competition The Amazing Race.

• List of rivers of Iceland
• Waterfalls of Iceland

• The Official Gullfoss website Archived 2014-09-24 at the Wayback Machine
• Live webcam located at Gullfoss Archived 2015-02-20 at the Wayback Machine
• Gullfoss gallery from islandsmyndir.is
• Gullfoss Gallery
• Gullfoss.org Information and photos of Gullfoss
• Gullfoss virtual tour Archived 2012-01-19 at the Wayback Machine