The Atlantic slave traders, ordered by trade volume, were: the Portuguese, the British, the French, the Spanish, and the Dutch Empire. Several had established outposts on the African coast where they purchased slaves from local African leaders.[5]

The First Atlantic system was the trade of enslaved Africans to, primarily, South American colonies of the Portuguese and Spanish empires; it accounted for slightly more than 3% of all Atlantic slave trade. It started (on a significant scale) in about 1502[40] and lasted until 1580 when Portugal was temporarily united with Spain. While the Portuguese were directly involved in trading enslaved peoples, the Spanish empire relied on the asiento system, awarding merchants (mostly from other countries) the license to trade enslaved people to their colonies. During the first Atlantic system most of these traders were Portuguese, giving them a near-monopoly during the era. Some Dutch, English, and French traders also participated in the slave trade.[41] After the union, Portugal came under Spanish legislation that prohibited it from directly engaging in the slave trade as a carrier. It became a target for the traditional enemies of Spain, losing a large share of the trade to the Dutch, English and French.

The Second Atlantic system was the trade of enslaved Africans by mostly English, Portuguese, French and Dutch traders. The main destinations of this phase were the Caribbean colonies and Brazil, as European nations built up economically slave-dependent colonies in the New World.[42] Slightly more than 3% of the enslaved people exported from Africa were traded between 1450 and 1600, and 16% in the 17th century.