苏维埃社会主义共和国联邦(Union of Soviet Socialist Republics (U.S.S.R.))，亦称苏联（Soviet Union）。

前共和国。跨欧洲东部和亚洲北部和中部。在其崩溃前共有十五个苏维埃社会主义共和国－－亚美尼亚、亚塞拜然、白俄罗斯、爱沙尼亚、乔治亚（今乔治亚共和国）、哈萨克、吉尔吉斯、拉脱维亚、立陶宛、摩尔多瓦、俄罗斯、塔吉克、土库曼、乌克兰和乌兹别克；还包括二十个苏维埃社会主义自治共和国－－俄罗斯十六个、乔治亚两个、亚塞拜然一个、乌兹别克一个。面积为22,400,000平方公里。首都莫斯科。疆土从波罗的海和黑海一直伸展到太平洋之滨。是世界上国土最大的国家。东西长约10,900公里，南北宽约4,500公里，占世界24个时区中的11个。边界临六个欧洲国家和六个亚洲国家。地形有肥沃的土地、沙漠、冻原、高山、一些世界最大的河流及最大的内陆水域，包括最大的里海。海岸线北冰洋绵延了4,825公里，太平洋1,610公里。农业、采矿及工业发达。

1917年俄国革命後，在前俄罗斯帝国的版图内建立起四个社会主义共和国：俄罗斯苏维埃社会主义联邦共和国、外高加索苏维埃社会主义联邦共和国、乌克兰苏维埃社会主义共和国和白俄罗斯苏维埃社会主义共和国。1922年，苏维埃社会主义共和国联邦建立在四个加盟共和国的基础上，在以後的年代更多的加盟共和国相继建立。列宁去世（1924）後，史达林击败其对手而获得政治领导权。1928年实施五年计画及加强工业化和农业集体化。1930年代末期进行清党（参阅purge trials），囚禁和处决上百万被认为对国家有危险的人。第二次世界大战後，苏联和美国两个集团间的长期紧张关系成了「冷战」。1940年代在东欧建立了共产集团。1949年制造原子弹。1953年第一次试爆氢弹。史达林去世後，赫鲁雪夫上台，他放松对政治和文化的一些严密控制。1957年发射第一颗人造卫星。在布里兹涅夫领导下，朝向自由化的部分倒转。1980年代中期戈巴契夫掌权，鼓吹新开放政策。1990年年底，共产主义政府瓦解，实行新的市场经济计画。1991年12月5日苏联正式解散（进一步讯息，请参见上述各独立共和国条目）。

English version：

Union of Soviet Socialist Republics (U.S.S.R.)

Former republic, eastern Europe and northern and central Asia. It consisted, in its final years, of 15 soviet socialist republics that gained independence at its dissolution: Armenia, Azerbaijan, Belorussia (now Belarus), Estonia, Georgia (now Republic of Georgia), Kazakhstan, Kirgiziya (now Kyrgyzstan), Latvia, Lithuania, Moldova, Russia, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan. It also contained 20 autonomous soviet socialist republics: 16 within Russia, 2 within Georgia, 1 within Azerbaijan, and 1 within Uzbekistan. Area: 8,649,512 sq mi (22,402,235 sq km). Capital: Moscow. Stretching from the Baltic and Black seas to the Pacific Ocean, the Soviet Union comprised the largest country on the globe, having a maximum east-west extent of about 6,800 mi (10,940 km) and a maximum north-south extent of about 2,800 mi (4,505 km). It encompassed 11 time zones and had common boundaries with 6 European countries and 6 Asian countries. Its regions contained fertile lands, deserts, tundra, high mountains, some of the world's largest rivers, and large inland waters, including most of the Caspian Sea. The coastline on the Arctic Ocean extended 3,000 mi (4,825 km), while that on the Pacific was 1,000 mi (1,610 km) long. It was an agricultural, mining, and industrial power. Following the Russian Revolution of 1917, four socialist republics were established on the territory of the former Russian empire: the Russian Soviet Federated Socialist Republic, the Transcaucasian Soviet Federated Socialist Republic, the Ukrainian Soviet Socialist Republic, and the Belorussian Soviet Socialist Republic. These four constituent republics established the Union of Soviet Socialist Republics in 1922, to which other republics were added over the years. A power struggle begun in 1924 with the death of Communist leader Vladimir Ilich Lenin ended in 1927 when Joseph Stalin gained victory. Implementation of the first of the Five-Year Plans in 1928 centralized industry and collectivized agriculture. A purge in the late 1930s resulted in the imprisonment or execution of millions of persons considered dangerous to the state (see Purge Trials). After World War II, with their respective allies, the U.S.S.R. and the U.S. engaged in the Cold War. In the late 1940s it brought about the establishment of Communist regimes throughout most of eastern Europe. The U.S.S.R. exploded its first atomic bomb in 1949, and its first hydrogen bomb in 1953. Following Stalin's death, it experienced limited political and cultural liberalization under Nikita Khrushchev. It launched the first manned orbital space flight in 1961. Under Leonid Brezhnev there was a partial reversal of the move towards liberalization. In the mid-1980s its leader Mikhail Gorbachev instituted a liberal policy of perestroika. By the end of 1990 the Communist government had toppled, and a program to create a market economy was implemented. The U.S.S.R. was officially dissolved on December 25, 1991. (For further information, see independent republics mentioned above.).