Sebastian Gramss is a German double bassist, cellist, and composer of jazz and contemporary music.

Gramss studied double bass at Conservatorium van Amsterdam and Hochschule für Musik Köln.

He is composing for various groups as well as for radio plays, drama, film soundtracks and ballet.

In 1993 Gramss founded the group Underkarl[1] with Frank Wingold (guitar), Lömsch Lehmann (saxophone), Dirk-Peter Kölsch (drums) and Nils Wogram (trombone), still active as of 2017.

He played with Frank Gratkowski, Tatsuya Nakatani, Rudi Mahal, Marilyn Crispell, Fred Frith, Tom Cora, Elliott Sharp, Peter Kowald, Taylor Ho Bynum, Zeena Parkins, Peter Brötzmann, Robert Dick, Karl Berger, Axel Dörner, Hannes Bauer, Heinz von Cramer, Terry Jenoure, Marjana Sadowska.