The Loki-Fögrufjöll (Icelandic pronunciation: [ˈlɔːcɪ-ˈfœɣrʏˌfjœtl̥] ⓘ volcanic system;[2] also known as Hamarinn [ˈhaːmarɪn] after its central volcano or Lokahryggur [ˈlɔːkaˌr̥ɪkːʏr̥]) is a subglacial volcano under the Vatnajökull glacier.

The subglacial volcano is found within the Bárðarbunga fissure volcanic system, but is outside the caldera of Bárðarbunga itself.

[3] Earthquake swarms associated with the volcano are separate in time and place from other swarms in the Bárðarbunga system.

[2] The fissure swarm extending south-west towards Torfajökull has not had recent earthquakes or erupted in the Holocene.

[2] A geothermally and seismically active ridge called Lokahryggur or the Loki Ridge,[2] extends eastward from Hamarinn under the ice to where in 1996 the Gjálp volcanic fissure erupted between Bárðarbunga and Grímsvötn and produced a large jökulhlaup.