Rac2 (Ras-related C3 botulinum toxin substrate 2) is a small (~21 kDa) signaling G protein (to be specific, a GTPase), and is a member of the Rac subfamily of the family Rho family of GTPases. It is encoded by the gene RAC2.

Members of Rho family of GTPases appear to regulate a diverse array of cellular events, including the control of cell growth, cytoskeletal reorganization, and the activation of protein kinases.