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" (including unoccupied dwellings and wasteland) 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.

Some street children, notably in more developed nations, are part of a subcategory called thrown-away children, consisting of children who have been forced to leave home. Thrown-away children are more likely to come from single-parent homes. Street children are often subject to abuse, neglect, exploitation, or, in extreme cases, murder by "clean-up squads" that have been hired by local businesses or police.