The Revolutions of 1917–1923 were a revolutionary wave that included political unrest and armed revolts around the world inspired by the success of the Russian Revolution and the disorder created by the aftermath of World War I. The uprisings were mainly socialist or anti-colonial in nature. Some socialist revolts failed to create lasting socialist states. The revolutions had lasting effects in shaping the future European political landscape, with for example the collapse of the German Empire and the dissolution of Austria-Hungary.

A revolutionary wave or revolutionary decade is one series of revolutions occurring in various locations within a similar time-span. In many cases, past revolutions and revolutionary waves have inspired current ones, or an initial revolution has inspired other concurrent "affiliate revolutions" with similar aims. The causes of revolutionary waves have become the subjects of study by historians and political philosophers, including Robert Roswell Palmer, Crane Brinton, Hannah Arendt, Eric Hoffer, and Jacques Godechot.