Betamethadol (INN), or ò-methadol, also known as betametadol, is a synthetic opioid analgesic. It is an isomer of dimepheptanol (methadol), the other being alphamethadol (ñ-methadol). Betamethadol is composed of two isomers itself, <small>L</small>-ò-methadol, and <small>D</small>-ò-methadol. Based on structure-activity relationships it can be inferred that both isomers are likely to be active as opioid analgesics, similarly to those of betacetylmethadol (ò-acetylmethadol).