Oscar Grönberg (born 19 April 1987, in Sweden), is a Swedish/Norwegian jazz musician (piano) based in Trondheim, Norway, known as bandleader of his own O. G. Trio/O.

Grönberg is a graduate of the Jazz program at Trondheim Musikkonsevatorium in 2011,[1] where he joined the Hanna Paulsberg Concept.

Together they create a world of groove, improvisation, humor and playful interaction, all based on Grönberg's subtle and original compositions.

The trio is at the same time deeply respectful of the compositions, but also irreverent and free in their interactions over the well-established and endangered species line.

The music is inspired by the likes of Thelonious Monk, Ahmad Jamal and Andrew Hill.