The Hvítá river is formed by the meltwater from the Lángjökull glacier pouring out of Hvítávatn lake to begin its journey to the sea. About 40 kilometers (25 miles) downstream the wide, rushing river suddenly turns and tumbles into a deep, narrow crevice set at an oblique angle to the original course, forming a truly spectacular waterfall in the process.

Gullfoss translates as "Golden Falls," and was so named because the high sediment content of glacial water makes it glow gold in the sunlight as it roars over the cataract. Gullfoss consists of three separate drops: a relatively gentle three-step staircase that begins the descent; and a two-stage waterfall with plunges of 11 meters (36 feet) and 21 meters (69 feet). The river then continues to flow south through a deep and narrow canyon with walls up to 70 meters (230 feet) high.

In the 20th century, Gullfoss was considered for hydroelectric development; although the property was leased by different interested parties, an actual project failed to materialize. There is a frequently-told story that attributes the unspoiled state of the site to Sigríður Tómasdóttir, the daughter of the leasor who worked tirelessly to block development and even threatened to jump to her death in the falls if a dam was built. This story does not seem to be true, but its popularity is such that a plaque overlooking the cascade honors her memory.

Today, Gullfoss is under the protection of the state, which maintains the falls in their natural state. This has proven to be a fairly successful arrangement, as Gullfoss is arguably Iceland's most popular waterfall, and undoubtedly one of the most popular tourist attractions in the country.