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) involving specific narcotic drugs and lays down a system of regulations (licenses, measures for treatment, research, etc.) for their medical and scientific uses, concluded under the auspices of the United Nations. The convention 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 three conventions establish the legal framework for international drug control.