Ketorfanol, or ketorphanol, is an opioid analgesic of the morphinan family that was found to possess "potent antiwrithing activity" in animal assays but was never marketed. It is a 17-cycloalkylmethyl derivative of morphinan and as such, is closely related structurally to butorphanol, cyclorphan, oxilorphan, proxorphan, and xorphanol, which act preferentially as κ-opioid receptor agonists and to a lesser extent as μ-opioid receptor partial agonists/antagonists.