Ungmennafelagio Fjolnir is an Icelandic football club based in Reykjavik. They currently feature in the Landsbankadeild, the Icelandic top flight.
Fjolnir were established in 1988. They gained promotion from the 1. deild karla in 2007 and finished 6th in the Icelandic first division in 2008.
Fjolnir play their home matches at the Fjolnisvollur that can accommodate 1000 spectators.