This paper is focusing on the ethnic, confessional and cultural background of regionalism in Russia. On the one hand, the historically evolved spatial structures are considered; on the other hand, the emphasis is made on transformation processes of the Post-Soviet period. The analysis covers: 1) the historical framework of ethnic settlement and ethnic identity patterns in Russia and their dynamics at the end of the 20th and beginning of the 21st centuries; 2) the linguistic diversity of the country and the linguistic division of the Russian Federation; 3) the spatial pattern of confessional groups in Russia; and 4) the phenomenon of regional/local identity as one of the key driving forces of regional development. The cultural space of Russia is characterized by mosaics of various regional and local communities; its transformation is still going on and entails the permanent genesis of new regional structures and clusters as well as some risks, tensions and threats. The "horizontal" socio-cultural differentiation of Russian space is based on huge discrepancies between various historical and cultural regions, their ethnic and regional diversity. The "vertical", hierarchical differentiation of cultural space is predominantly characterized by the increasing stratification of various population groups within the Russian regions. The inherited spatial patterns predominate both in ethnic settlement structures and in configurations of regional identity and cultural distinctions. Nevertheless, changes in the cultural geographic pattern could also be observed in the investigated period. The growing share of "titular" ethnic groups in the total population of national republics of Russia, as well as their growing concentration within the corresponding national units were the main trends in ethnic-geographical redistribution of population in the Russian Federation between 1990 and 2016.