Fagradalsfjall (Icelandic: [ˈfaɣraˌtalsˌfjatl̥] (listen)) is a tuya volcano formed in the Last Glacial Period on the Reykjanes Peninsula, around 40 kilometres (25 mi) from Reykjavík, Iceland. Fagradalsfjall is also the name for the wider volcanic system covering an area 5 kilometres (3 mi) wide and 16 kilometres (10 mi) long between the Svartsengi [ˈsvar̥(t)sˌeiɲcɪ] and Krýsuvík systems. The highest summit in this area is Langhóll [ˈlauŋkˌhoutl̥] (385 m (1,263 ft)). No volcanic eruption had occurred for 815 years on the Reykjanes Peninsula until 19 March 2021 when a fissure vent appeared in Geldingadalir to the south of Fagradalsfjall mountain. The 2021 eruption was effusive and continued emitting fresh lava sporadically until 18 September 2021.

The eruption was unique among the volcanoes monitored in Iceland so far and it has been suggested that it may develop into a shield volcano. Due to its relative ease of access from Reykjavík, the volcano has become an attraction for local people and foreign tourists. Another eruption, very similar to the 2021 eruption, began on 3 August 2022. It is still considered ongoing, although there has been no visible activity since 21 August 2022.