Pentagestrone (), also known as 17ñ-hydroxyprogesterone 3-cyclopentyl enol ether, is a steroidal progestin of the 17ñ-hydroxyprogesterone group that was never marketed. An acetate ester, pentagestrone acetate (Gestovis, Gestovister), has been marketed for clinical use. Pentagestrone was described in the literature in 1960.