Billy Greer is an American musician who was the bass guitarist for the rock band Kansas from 1985 to 2024. He joined the band when they reformed, making his debut appearance on 1986's Power. He had previously worked with Kansas keyboardist/vocalist Steve Walsh in the band Streets, and works with his own band Seventh Key when not performing with Kansas. He also was a member of the 2009 Kansas side project Native Window along with Kansas members Phil Ehart, Richard Williams, and David Ragsdale.