Steinar Sønk Nickelsen (born 5 October 1978) is a Norwegian jazz musician (Hammond organ and piano) from Bærum, known from several bands and album releases.

In Oslo he played in a trio with Pål Thowsen and Jon Eberson releasing the album (2002).After this he attended the jazz program at Trondheim Musikkonservatorium, joined the Trondheim Jazz Orchestra and recorded with Pat Metheny.

Moreover, he collaborated in the band Jupiter with Håvard Stubø and Magnus Forsberg who released several albums.

In Peloton he played with the guitarist Petter Vågan, the drummer Erik Nylander, saxophonist Hallvard Godal and trumpeter Karl Strømme.

He moved to Copenhagen (2004) for studies at the Rhythm Conservatory, where he led the Nickelsen Trio with drummer Ari Hoenig and guitarist Lage Lund at the time.