The 1930s (pronounced "nineteen-thirties" and commonly abbreviated as "the '30s" or "the Thirties") was a decade that began on January 1, 1930, and ended on December 31, 1939. In the United States, the Dust Bowl led to the nickname the "Dirty Thirties".

The decade was defined by a global economic and political crisis that culminated in the Second World War. It saw the collapse of the international financial system, beginning with the Wall Street Crash of 1929, the largest stock market crash in American history. The subsequent economic downfall, called the Great Depression, had traumatic social effects worldwide, leading to widespread poverty and unemployment, especially in the economic superpower of the United States and in Germany, which was already struggling with the payment of reparations for the First World War. The Dust Bowl in the United States (which led to the nickname the "Dirty Thirties") exacerbated the scarcity of wealth. U.S. President Franklin D. Roosevelt, who took office in 1933, introduced a program of broad-scale social reforms and stimulus plans called the New Deal in response to the crisis. The Soviet Union's second five-year plan gave heavy industry top priority, putting the Soviet Union not far behind Germany as one of the major steel-producing countries of the world, while also improving communications. First-wave feminism made advances, with women gaining the right to vote in South Africa (1930, whites only), Brazil (1933), and Cuba (1933). Following the rise of Adolf Hitler and the emergence of the NSDAP as the country's sole legal party in 1933, Germany imposed a series of laws which discriminated against Jews and other ethnic minorities.