Social-imperialism is imperialism with a socialist (communist) face. Marxists apply the term to countries that they see as having betrayed socialism and turned themselves into hegemons that exploit other countries. Because Marxist theory is opposed to empire, the accusation of social-imperialism implies that the country so accused has ceased to be socialist and has returned to capitalism in practice, even if it appears socialist on the surface. The term is often summed up as meaning "socialist in words, imperialist in deeds".

Maoist China famously called the Soviet Union social-imperialist in the years leading up to the Sino–Soviet split, arguing that the Soviet Union had come to dominate and exploit the smaller countries in its sphere to the point of organising their economies around Soviet, not domestic, needs, making them into dependent banana republics whose governments toed the Soviet line. China thus saw the Soviet Union as having become a non-socialist empire shortly after the death of Stalin and of being the socialist world's equivalent of a colonialist or imperialist country in the First World.