Lens barrel, camera body, camera system

A camera system and a lens barrel are provided in an exchangeable-lens camera including a shake correction mechanism that integrally drives a lens barrel and an imaging unit, it being possible for lenses to be exchanged smoothly, and greater utility and convenience to be obtained. A lens barrel to and from which a camera body can be attached and detached, wherein the lens barrel includes: a first barrel having a first engagement part that engages with a first part of the camera body; a second barrel disposed inside the first barrel, the second barrel having a second engagement part that engages with a second part of the camera body, and having an optical system; and a drive unit that drives the second barrel in relation to the first barrel.