Øystein Greni (born 15 June 1974 in Oslo) is the frontman and chief songwriter of the Norwegian rock band Bigbang.

Greni founded the band in 1992 and has been the only constant member since its formation.

In 1992, Greni, Erik Tresselt and Christer Engen formed Bigbang which has since established its position as one of the principal rock acts of Norway.

As the only consistent member throughout the band's history, Bigbang's success is often attributed to Greni's skills as a guitarist and songwriter.

In 2003, he produced the EP debut of Latin performer Maria Orieta (Greni's fiancée) Buenos Aires via the Grandsport Records indie label.