Siwan Rhys is a pianist devoted to contemporary music and collaboration with composers and other artists.

She has played at prestigious British venues such as the Wigmore Hall, Royal Festival Hall, Barbican Hall, St David's Hall, Symphony Hall, and abroad at the Concertgebouw Amsterdam, Carnegie Hall, Elbphilharmonie Hamburg, Tokyo Opera City, Philharmonie de Paris, Shanghai Symphony Hall, Philharmonie Luxembourg, Esplanade Singapore and others. She has also appeared at the BBC Proms, Huddersfield Contemporary Music Festival, Aldeburgh Festival, Cheltenham Festival, London Contemporary Music Festival, and has recorded many times for television, radio, and for labels such as NMC, all that dust, Another Timbre, Classical Remix, and Prima Facie.

Recent releases include a critically-acclaimed recording of Stockhausen's KONTAKTE and of Oliver Leith's good day good day bad day bad day with GBSR Duo, a re-voicing by Mira Calix of John Cage's Sonatas and Interludes, solo piano music by Ryoko Akama, a Barbara Monk Feldman portrait disc, and Steve Reich's Music for 18 Musicians with Colin Currie Group.

Siwan is a member of piano-percussion duo GBSR Duo and new music group Explore Ensemble. Also a regular ensemble and orchestral pianist, Siwan has worked with the London Sinfonietta, Colin Currie Group, LA Phil New Music Group, Birmingham Contemporary Music Group, Riot Ensemble, Clod Ensemble, London Symphony Orchestra, Philharmonia Orchestra, City of Birmingham Symphony Orchestra, and BBC National Orchestra of Wales.

She is an honorary member of the Welsh Gorsedd of Bards, and teaches at the London Contemporary School of Piano.