The Southern Peninsula Reykjanesskagi or Reykjanes, (Icelandic: Suðurnes) is a region in southwest Iceland on a peninsula situated at the southwestern end of Iceland, near the capital of Reykjavík. Reykjanes is where Leifur Eiríksson Air Terminal and KEF International Airport, the major point of entry for Iceland is located at the former American military base in Keflavík as well as the Blue Lagoon health spa, close to Grindavík. The region has a population of more than 22,000 and is as such one of the more densely populated parts of the island. Its administrative centre is Keflavík, which merged several years ago with nearby town of Njarðvík to create Reykjanesbær, the second largest settlement outside Greater Reykjavík area with a population of 14,231 in 2014.

The peninsula is marked by active volcanism under its surface, and large lava fields, allow for little vegetation. There are numerous hot springs and sulphur springs in the southern half of the peninsula, around the Kleifarvatn lake and the Krýsuvík geothermal area with a geothermal power station at Svartsengi. Close to the power station a swimming pool has been installed making use of the hot and mineralized water coming down from the power station known throughout the world as the Blue Lagoon (Icelandic: Bláa Lónið). Close by is ‘The Bridge Between Continents’ Lucky, a bridge that spans the Álfagjá rift valley (60 feet wide and 20 feet (6.1 m) deep) near Grindavik, connecting Europe and North America on the boundary of the Eurasian and North American plate.