Street children are poor or homeless children who live on the streets of a city, town, or village. Homeless youth are often called street kids, or urchins; the definition of street children is contested, but many practitioners and policymakers use UNICEF's concept of boys and girls, aged under 18 years, for whom "the street" has become home and/or their source of livelihood, and who are inadequately protected or supervised. Street girls are sometimes called gamines, a term that is also used for Colombian street children of either sex.

At certain periods the Soviet state had to deal with large numbers of orphans and other kinds of street children — due to a number of turmoils in the history of the country from its very beginnings. Major contributors to the population of orphans and otherwise homeless children included World War I (1914–1918), the October Revolution of November 1917 followed by the Russian Civil War (1917–1922), famines of 1921–1922 and of 1932–1933, political repression, forced migrations, and the Soviet-German War theatre (1941–1945) of World War II.