Foetus is the primary musical outlet of J. G. Thirlwell. Until 1995 the band underwent various name changes, all including the word foetus. Monikers adopted at different times include Foetus Under Glass, You've Got Foetus on Your Breath and Scraping Foetus Off The Wheel. After 1995 the name permanently became Foetus, though the related project The Foetus Symphony Orchestra was founded in 1997 and continues.

Thirlwell acts as the sole instrumentalist, vocalist, songwriter and producer for all Foetus works and as such is the only member of the band. Other artists may occasionally collaborate with Thirlwell on Foetus works but are not considered members of Foetus. Thirlwell is solely responsible for the musical output of the band.