The Weimar Coalition is the name given to the coalition of the Social Democratic Party of Germany (SPD), the German Democratic Party (DDP), and the Catholic Centre Party, who together had a large majority of the delegates to the Constituent Assembly which met at Weimar in 1919, and were the principle groups which designed the constitution of Germany's Weimar Republic. These three parties were seen as the most committed to Germany's new democratic system, and together governed Germany until the elections of 1920, when the first elections under the new constitution were held, and both the SPD and especially the DDP lost a considerable share of their votes. Although the Coalition was revived in the ministry of Joseph Wirth from 1921 to 1922, the pro-Democratic elements never truly had a majority in the Reichstag from this point on, and the situation gradually grew worse with the continued weakening of the DDP. This meant that any pro-republican grouping which hoped to attain a majority would need to form a "Grand Coalition" with the more conservative German People's Party.

Nevertheless, the grouping remained at least theoretically important as the grouping of parties most supportive of republican government in Germany, and continued to act in coalition in the government of Prussia and other states until as late as 1932.