Slavery and forced labor, two of humanity's oldest institutions, were among the defining characteristics of colonial practice and understanding their demise is vital for understanding decolonization. Between 1500 and the mid-nineteenth century, “What moved in the Atlantic in these centuries was predominantly slaves, the output of slaves, the inputs to slave societies, and the goods and services purchased with the earnings on slave products.” Forced labor was also important in the economic development of African colonies. Africans, forcefully recruited, were often the mainstay of the troops of colonial conquest, and forced laborers built the roads, bridges, and railways that took out the commodities produced by forced labor. Since colonizers were too few or unwilling to do the work required to maintain and expand colonial holdings, and the colonized often wanted little or nothing to do with the colonizer, none of these colonies would have endured without unfree labor. That it was legitimate for the main part of the required labor to be performed by slaves or forced laborers was the dominant belief and assumption for most of the era of colonialism.

The abolition of slavery and amelioration of forced labor are relevant for understanding the end of colonialism in several respects.