The Convention on Psychotropic Substances is signed at Vienna.

The Convention on Psychotropic Substances of 1971 is a United Nations treaty designed to control psychoactive drugs such as amphetamine-type stimulants, barbiturates, benzodiazepines, and psychedelics signed in Vienna, Austria on 21 February 1971. The Single Convention on Narcotic Drugs of 1961 did not ban the many newly discovered psychotropics, since its scope was limited to drugs with cannabis, coca and opium-like effects.

Vienna is the capital, most populous city, and one of nine states of Austria. It is Austria's primate city, with just over two million inhabitants. Its larger metropolitan area has a population of nearly 2.9 million, representing nearly one-third of the country's population. Vienna is the cultural, economic, and political center of the country, the fifth-largest city by population in the European Union, and the most populous of the cities on the river Danube.