Gregor Strasser was a German politician and early leader of the Nazi Party. Along with his younger brother Otto, he was a leading member of the party's left-wing faction, which brought them into conflict with the dominant faction led by Adolf Hitler, resulting in his murder in 1934. The brothers' strand of the Nazi ideology is known as Strasserism.

The Nazi Party, officially the National Socialist German Workers' Party, was a far-right political party in Germany active between 1920 and 1945 that created and supported the ideology of Nazism. Its precursor, the German Workers' Party, existed from 1919 to 1920. The Nazi Party emerged from the extremist German nationalist, racist and populist Freikorps paramilitary culture, which fought against communist uprisings in post–World War I Germany. The party was created to draw workers away from communism and into völkisch nationalism. Initially, Nazi political strategy focused on anti–big business, anti-bourgeois, and anti-capitalist rhetoric; it was later downplayed to gain the support of business leaders. By the 1930s, the party's main focus shifted to antisemitic and anti-Marxist themes. The party had little popular support until the Great Depression, when worsening living standards and widespread unemployment drove Germans into political extremism.