The Republics of the Soviet Union or the Union Republics of the Soviet Union were administrative units that report directly to the Government of the Soviet Union.^[1] The Soviet Union was a highly centralized state.

Map of the Union Republics from 1956-1991
Soviet socialist republic	member since	population (1989)	pop./ USSR pop. (%)	area (km²) (1991)	area/ USSR area (%)	capital	independent state	No.
Russian Soviet Federative Socialist Republic	1922	147,386,000	51.40	17,075,400	76.62	Moscow	Russia	1
Ukrainian Soviet Socialist Republic	1922	51,706,746	18.03	603,700	2.71	Kiev (Kharkov before 1934)	Ukraine	2
Uzbek Soviet Socialist Republic	1924	19,906,000	6.94	447,400	2.01	Tashkent (Samarkand before 1930)	Uzbekistan	4
Kazakh Soviet Socialist Republic	1936	16,711,900	5.83	2,727,300	12.24	Alma-Ata	Kazakhstan	5
Byelorussian Soviet Socialist Republic	1922	10,151,806	3.54	207,600	0.93	Minsk	Belarus	3
Azerbaijan Soviet Socialist Republic	1936	7,037,900	2.45	86,600	0.39	Baku	Azerbaijan	7
Georgian Soviet Socialist Republic	1936	5,400,841	1.88	69,700	0.31	Tbilisi	Georgia	6
Tajik Soviet Socialist Republic	1929	5,112,000	1.78	143,100	0.64	Dushanbe	Tajikistan	12
Moldavian Soviet Socialist Republic	1940	4,337,600	1.51	33,843	0.15	Kishinev	Moldova	9
Kirghiz Soviet Socialist Republic	1936	4,257,800	1.48	198,500	0.89	Frunze	Kyrgyzstan	11
Lithuanian Soviet Socialist Republic	1940	3,689,779	1.29	65,200	0.29	Vilnius	Lithuania	8
Turkmen Soviet Socialist Republic	1924	3,522,700	1.23	488,100	2.19	Ashkhabad	Turkmenistan	14
Armenian Soviet Socialist Republic	1936	3,287,700	1.15	29,800	0.13	Yerevan	Armenia	13
Latvian Soviet Socialist Republic	1940	2,666,567	0.93	64,589	0.29	Riga	Latvia	10
Estonian Soviet Socialist Republic	1940	1,565,662	0.55	45,226	0.20	Tallinn	Estonia	15