Russification (Russian: русификация, romanized: rusifikatsiya), or Russianization, is a form of cultural assimilation in which non-Russians, whether involuntarily or voluntarily, give up their culture and language in favor of the Russian culture and the Russian language.

In a historical sense, the term refers to both official and unofficial policies of the Russian Empire and the Soviet Union with respect to their national constituents and to national minorities in Russia, aimed at Russian domination and hegemony.

The major areas of Russification are politics and culture. In politics, an element of Russification is assigning Russian nationals to lead administrative positions in national institutions. In culture, Russification primarily amounts to the domination of the Russian language in official business and the strong influence of the Russian language on national idioms. The shifts in demographics in favour of the ethnic Russian population are sometimes considered a form of Russification as well.

Analytically, it is helpful to distinguish Russification, as a process of changing one's ethnic self-label or identity from a non-Russian ethnonym to Russian, from Russianization, the spread of the Russian language, culture, and people into non-Russian cultures and regions, distinct also from Sovietization or the imposition of institutional forms established by the Communist Party of the Soviet Union throughout the territory ruled by that party. In this sense, although Russification is usually conflated across Russification, Russianization, and Russian-led Sovietization, each can be considered a distinct process. Russianization and Sovietization, for example, did not automatically lead to Russification – a change in language or self-identity of non-Russian people to being Russian. Thus, despite long exposure to the Russian language and culture, as well as to Sovietization, at the end of the Soviet era, non-Russians were on the verge of becoming a majority of the population in the Soviet Union.