The Single Convention on Narcotic Drugs, 1961 (Single Convention, 1961 Convention, or C61) is an international treaty that controls activities (cultivation, production, supply, trade, transport) of specific narcotic drugs and lays down a system of regulations (licenses, measures for treatment, research, etc.) for their medical and scientific uses; it also establishes the International Narcotics Control Board.
The Single Convention was adopted in 1961 and amended in 1972. As of 2022, the Single Convention as amended has been ratified by 186 countries. The convention has since been supplemented by the 1971 Convention on Psychotropic Substances, which controls LSD, MDMA, and other psychoactive pharmaceuticals, and the 1988 United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
The Single Convention as amended in 1972 had been ratified or acceded to by 186 states. Only Chad remained party to the original 1961 Convention in its unamended form. The Cook Islands, Equatorial Guinea, Kiribati, Nauru, Niue, Samoa, South Sudan, Timor-Leste, Tuvalu, and Vanuatu are not parties.
Since the Single Convention is not self-executing, parties must enact legislation to carry out its provisions, and the UNODC works with countries' legislatures to ensure compliance.
The League of Nations adopted several drug control treaties prior to World War II, such as the International Opium Convention, and International Convention relating to Dangerous Drugs (1925) specifying uniform controls on addictive drugs such as cocaine and opium, and its derivatives. However, the lists of controlled substances were fixed in the treaties' text. Consequently, it was necessary to periodically amend or supersede the conventions with the introduction of new treaties to keep up with advances in chemistry. According to a 1954 interview with United States Commissioner of Narcotics Harry J. Anslinger, the cumbersome process of conference and state-by-state ratification could take many decades.