Lars Petter Hagen (born 2 August 1975) is a Norwegian contemporary composer, former director of the Ultima Oslo Contemporary Music Festival and currently an adviser for the Oslo Philharmonic Orchestra.
He received a 2013 Spellemannprisen Award in the Composer category for a release with the Oslo Philharmonic, Rolf Gupta and Gjermund Larsen featuring his works.
Hagen has also served as artistic director for Ny Musikk (the Norwegian section of the ISCM) and festivals Happy Days, Nordic Music Days and the Ultima Oslo Contemporary Music Festival.
Hagen was appointed as permanent artistic director for the Ultima Festival in 2012, after having held the position on a temporary basis in 2009 and 2010.
2012 saw Hagen releasing the album Elements of Light with German electronica producer Pantha du Prince and ensemble The Bell Laboratory.