Located on the western coast of central Africa and south of the Congo River (formerly known as the Zaire River), the kingdom arose in the late 14th century CE following the alliance of several local principalities which had been in existence since the second half of the first millennium CE. Kongo, dominated by Bantu-speaking peoples, had its capital at Mbanza Kongo - known to the Kongolese as Banza, meaning 'residence of the king' - which was located on a fertile and well-watered plateau just below the western end of the Congo River. The kingdom expanded its territory further by a gradual process of military conquest, probably motivated above all by a desire to acquire slaves.

The kingdom of Kongo was highly centralised and ruled by a single monarch or nkani who appointed regional governors throughout his territory. These governors, in turn, appointed local officials and collected tribute such as ivory, millet, palm wine, and leopard and lion skins from local chiefs, which were passed on to the king at Mbanza Kongo. Tributes were paid at lavish annual ceremonies which involved much feasting and beer-drinking. In return for their offerings, chiefs and officials received the king's favour, military protection, and some material rewards such as food delicacies and clothing. There was, too, a certain religious aspect to tribute payment as it was considered a way to maintain divine favour as well as a royal one.

From 1470 and the Portuguese colonization of Sao Tome and Principe, islands off the coast, there was a boom in Kongo's slave markets. In return, the Kongolese received cotton clothing, silk, glazed china, glass mirrors, knives and glass beads. The consumption of these luxuries was highly controlled by the king so that only the elite he favoured had access to them.

Some Kongo kings converted to Christianity, the first being King Affonso I (r. 1506-1543 CE), following the efforts of Christian missionaries who first arrived in the region in 1491 CE. The new religion with its strange but glittering ceremonies and the implied association with the wealthy European traders enhanced the prestige of the king in the eyes of his people. Catholicism was established as the official religion of the royal household, the capital was renamed Sao Salvador, churches were built, and Affonso even successfully invited the Pope to permit the appointment of a Kongo bishop. During the second half of the 17th century CE, Christianity received a further boost in the region when Italian Capuchin missionaries set their sights on Kongo. The religion would have a lasting effect on art in the kingdom, which incorporated such elements as the cross and European conventions of proportion, mixing these with the indigenous passion for stylization and geometric decoration to produce distinctive statues, pottery, masks and relief carvings in all materials from copper to ivory, as well as woven fabrics.

Besides religion, the Portuguese brought technical knowledge (masonry, carpentry, and stock-breeding) and crops from the Americas such as maize, cassava, and tobacco as part of a grand plan to westernise Kongo and make it both a valuable trading partner and a secure base from which to conquer large swathes of central Africa. In the event, though, and just like other areas of the continent where the Portuguese were involved, the greed and inept political and religious interference of the Europeans only brought both their own and the local regime's downfall.

Relations soured when the Portuguese, based on the island of Sao Tome, began to cut out the Kongo king and launch their own raids to grab slaves from Africa's interior or they simply kidnapped the Kongolese themselves. Slaves were now needed in huge numbers to work the sugarcane plantations on Sao Tome and in Brazil. The Portuguese also sought to control the kingdom's copper mines, impose their own system of laws, and convert the people to Christianity, not just the elite. The Kongo kings, similarly, saw the value of eliminating the Portuguese in their trade affairs and knew that by building their own fleet they could ship goods themselves to the waiting market in Europe. So began a tussle between the two sides who became increasingly distrustful of each other's intentions. The Kongo kings began to realise that the unregulated abduction of slaves and spread of Christianity - even if the local brand of that religion incorporated and co-existed with ancient indigenous beliefs - was undermining their traditional authority as the political, religious, and economic leader of the kingdom.