Thridrangaviti Lighthouse, Lighthouse in Southern Region, Iceland.

Thridrangaviti is a lighthouse in the Southern Region of Iceland, standing on a narrow rock pillar that rises from the Atlantic. The concrete structure reaches four meters in height and features exterior walls designed to withstand constant sea wind and spray.

Workers began construction in 1938, drilling holes into the solid rock to secure iron chains for hoisting materials to the summit. The building was completed in 1939 and switched from petroleum lamps to solar power in 1993.

The name Þrídrangar means "three rock pillars", after Stóridrangur (the stack bearing the lighthouse), Þúfudrangur and Klofadrangur. The light's beam is a long white flash then a short white flash, Morse code for N, every 30 seconds. In 2009 photographs by Árni Sæberg in Morgunblaðið spread worldwide after Justin Bieber reposted one; the band KALEO filmed a music video on the helipad on 5 July 2020.

The lighthouse is reached by helicopter to a helipad added in the 1950s; a difficult stairway cut into the rock leads down to a pier at sea level. The climb to the 36.5-metre summit was originally made with drills, hammers and chains fixed into the basalt.

The three sea stacks are named Stóridrangur, Þúfudrangur and Klofadrangur; the lighthouse stands on Stóridrangur. In 2009 photographs by Árni Sæberg, published in Morgunblaðið, reached a worldwide audience after Justin Bieber shared one. The Icelandic band KALEO filmed a music video on the helipad on 5 July 2020, the light's 78th anniversary.