Slavery is a system under which people are treated as property to be bought and sold, and are forced to work. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation. Historically, slavery was institutionally recognized by many societies; in more recent times slavery has been outlawed in most societies but continues through the practices of debt bondage, indentured servitude, serfdom, domestic servants kept in captivity, certain adoptions in which children are forced to work as slaves, child soldiers, and forced marriage.

Slavery predates written records and has existed in many cultures. The number of slaves today is higher than at any point in history, remaining as high as 12 million to 27 million, though this is probably the smallest proportion of the world's population in history. Most are debt slaves, largely in South Asia, who are under debt bondage incurred by lenders, sometimes even for generations. Human trafficking is primarily used for forcing women and children into sex industries.