Koshi Yamada (山田晃士, Yamada Koshi) is a Japanese singer and guitarist who performs music that fuses elements of gypsy jazz, cabaret, swing, chanson and occasionally rock. He began as one of the vocalists for the metal band AROUGE. Once AROUGE disbanded, Yamada went solo. In 1997 he formed the group KOSHI au Bourbier, "to express borderless music revue."
Yamada has released albums under various names and collaborations, including: