Ungmennafélagið Fjölnir, commonly known as Fjölnir, is a multi-sport club from Iceland. The club is located in Grafarvogur, Reykjavík. The club was founded in 1988 under the original name Ungmennafélagið Grafarvogur; however, because another team already had the abbreviation UMFG, the name was changed to Ungmennafélagið Fjölnir, commonly referred to as Fjölnir. A total of nine sports are practised at the club: football, basketball, handball, taekwondo, karate, tennis, swimming, athletics and gymnastics. Chess is also played at the club. Each one of these sports has their own department with their own board but all are under the main board and the club office.

Fjolnir ženy je ženský futbalový klub z mesta Reykjavík na Islande. Klub bol založený v roku 2010 a v súčasnosti hrá v Islandskeij kvenna 1. deild, druhej najvyššej islandskéj futbalovej lige žien. Domovským štadiónom klubu je stadion Fjölnisvöllur.