National delimitation in the Union of Soviet Socialist Republics was the process of specifying well-defined national territorial units (Soviet socialist republics – SSR, autonomous Soviet socialist republics – ASSR, autonomous oblasts (provinces), raions (districts) and "okrugs") from the ethnic diversity of the Union of Soviet Socialist Republics (USSR) and its subregions. The Russian-language term for this Soviet state policy was "razmezhevanie" (, "natsionalno-territorialnoye razmezhevaniye"), which is variously translated in English-language literature as "national-territorial delimitation" (NTD), "demarcation", or "partition". National delimitation formed part of a broader process of changes in administrative-territorial division, which also changed the boundaries of territorial units, but was not necessarily linked to national or ethnic considerations.