(“Trans-Siberian Main Railroad”), the longest single rail system in Russia, stretching from Moscow 5,778 miles (9,198 km) east to Vladivostok or (beyond Vladivostok) 5,867 miles (9,441 km) to the port station of Nakhodka. It had great importance in the economic, military, and imperial history of the Russian Empire and the Soviet Union.

Conceived by Tsar Alexander III, the construction of the railroad began in 1891 and proceeded simultaneously in several sections—from the west (Moscow) and from the east (Vladivostok) and across intermediate reaches by way of the Mid-Siberian Railway, the Transbaikal Railway, and other lines. Originally, in the east, the Russians secured Chinese permission to build a line directly across Manchuria (the Chinese Eastern Railway) from the Transbaikal region to Vladivostok; this trans-Manchurian line was completed in 1901. After the Russo-Japanese War of 1904–05, however, Russia feared Japan's possible takeover of Manchuria and proceeded to build a longer and more difficult alternative route, the Amur Railway, through to Vladivostok; this line was completed in 1916. The Trans-Siberian Railroad thus had two completion dates: in 1904 all the sections from Moscow to Vladivostok were linked and completed running through Manchuria; in 1916 there was finally a Trans-Siberian Railroad wholly within Russian territory. The completion of the railroad marked the turning point in the history of Siberia, opening up vast areas to exploitation, settlement, and industrialization.

The trans-Manchurian line came under full Chinese control only after World War II; it was renamed the Chinese Ch'ang-ch'un Railway. In the Soviet Union, over the years, a number of spur lines have been built radiating from the main trans-Siberian line. From 1974 to 1989 construction was completed on a large alternative route, the Baikal-Amur Mainline; its route across areas of taiga, permafrost, and swamps, however, has made upkeep difficult.

The full rail trip on the passenger train Rossiya from Moscow to Nakhodka (including a compulsory overnight stay in Khabarovsk) now takes about eight days.