The dominant form of government in Eastern Europe in the 1920s and 1930s was

The dominant form of government in Eastern Europe in the 1920s and 1930s varied by country, but many of these nations experienced a shift towards authoritarianism and dictatorship. Initially, after World War I, several countries in Eastern Europe adopted democratic forms of government as they gained independence or reorganized their political systems. However, this period of democracy was often short-lived.

During the 1920s, some of these countries faced significant economic, political, and social challenges, which along with the Great Depression, led to political instability. This instability made it easier for authoritarian leaders to seize control. By the 1930s, many Eastern European states had authoritarian or totalitarian regimes. Governmental forms ranged from right-wing nationalism to military dictatorships and, in some cases, monarchies that had been reinstated or strengthened to counteract the political chaos. Examples include Poland under the Sanacja regime, Yugoslavia under King Alexander's dictatorship, and Hungary under the regency of Admiral Miklós Horthy. The spread of fascism in Italy and National Socialism in Germany also influenced some of these governments.

One significant exception in the region was Czechoslovakia, which retained a functioning democracy until its occupation by Nazi Germany in 1938-1939. The rise of the Soviet Union also influenced the politics of the region, although the full Soviet domination of Eastern Europe would not occur until after World War II.