The United States abandoned gold convertibility for international transactions in 1971. On 15 August that year, President Richard Nixon announced the suspension of the dollar’s convertibility into gold for foreign governments and central banks.
This decision became known as the Nixon shock and effectively closed the “gold window” that had operated under the Bretton Woods system. Since 1944, participating countries had generally pegged their currencies to the U.S. dollar, while the United States promised to exchange official foreign-held dollars for gold at $35 per troy ounce.
The arrangement came under pressure as overseas dollar holdings grew, U.S. balance-of-payments deficits widened, and American gold reserves fell relative to claims on them. Nixon described the move as temporary, but the old system was not restored. The Smithsonian Agreement briefly adjusted exchange rates later in 1971, before the fixed-rate framework collapsed.
The date can be confused with 1933, when the United States ended domestic gold convertibility for ordinary citizens during the Great Depression. This question specifies international transactions, making 1971 the precise answer.