Hydromadinone (INN), also known as 6ñ-chloro-17ñ-hydroxyprogesterone, is a steroidal progestin of the 17ñ-hydroxyprogesterone group which was patented in 1967 but was never marketed. The C17ñ acetate ester of hydromadinone, hydromadinone acetate, also exists, but similarly was never marketed.