The Union of Russian National Communities (SRNO) was the largest Russian national organization in the White South of Russia during the Civil War. Unfortunately, its activities and ideology are practically not studied, and the works that mention it often contain numerous errors. The SRNO emerged in Melitopol at the turn of 1917-1918. Three factors played an important role in the course of its further development: 1) General M.G. Drozdovsky's detachment, 2) parochial public, 3) Carpatho-Russian organizations located in Rostov-on-Don after the retreat from Galicia. While in Melitopol during his march from Romania to the Don, General M.G. Drozdovsky entered into close contact with the local Russian national community and its founder P.I. Kvita. Their relationship lasted until General's death. The parochial organizations (both Orthodox and Old Believers) also played a significant role in the expansion of the SRNO. The SRNO branch in Rostov-on-Don, the virtual capital of the White South, was created with the assitance of the members of the Galician-Russian organizations. Since the SRNO was a union of various organizations (parochial, Carpatho-Russian, monarchist), it was not so easy to develop a common political line, but its leadership sought to show its commitment to the “Russian progressive-national idea.” After General A.I. Denikin's defeat in 1920, the “national communities” moved their activities to the Crimea, where the SRNO was the only mass and prominent organization of Russian nationalists during the sping and summer of 1920.