Mbanza Kongo (Portuguese pronunciation: [ɐ̃ˈbɐ̃zɐ], [ĩˈbɐ̃zɐ], [mɨˈβɐ̃zɐ] or [miˈβɐ̃zɐ ˈkõɡu], known as São Salvador in Portuguese from 1570 to 1976; Kongo: Mbânza Kôngo) is the capital of Angola's northwestern Zaire Province with a population of 221,141 in 2024. Mbanza Kongo was the capital of the Kingdom of Kongo since its foundation before the arrival of the Portuguese in 1483 until the abolition of the kingdom in 1915, aside from a brief period of abandonment during civil wars in the 17th century. In 2017, Mbanza Kongo was declared a UNESCO World Heritage Site.

Mbanza Kongo (formerly called Nkumba a Ngudi, Mongo wa Kaila and Kongo dia Ngunga ) was founded by the first manikongo, Lukeni, at a junction of major trade routes. The Kingdom of Kongo at its peak reached from southern Africa's Atlantic coast to the Nkisi River. The Manikongo was chosen by clan leaders to rule some 300 square miles, an area that is part of several countries today. The Portuguese who first reached it in 1491 travelled ten days to get there from the mouth of the Congo River.

The earliest documented kings referred to their city in their correspondence as "the city of Congo" (cidade do Congo), and the name of the city as São Salvador appears for the first time in the letters of Álvaro I of Kongo (1568–1587) and was carried on by his successors.

When the Portuguese arrived in Kongo, Mbanza Kongo was already a large town, perhaps the largest in sub-equatorial Africa, and a letter from the Portuguese ambassador to Lisbon compared the size of the city (inside the inner walls) to the Portuguese town of Évora.

By the 1550s Mbanza Kongo hosted a community of Portuguese traders and Jesuit missionaries who conspired together in an attempted overthrow of the manikongo Diogo I Nkumbi a Mpudi.

In 1568 the manikongo Alvaro I was driven from Mbanza Kongo by the invading Jagas, who sacked the city. Alvaro managed to reclaim the capital with Portuguese military help, but had to yield Luanda, source of the nzimbu currency used in the kingdom, to them in payment.

During the reign of Afonso II, stone buildings were added, including a palace and several churches. Mbanza Kongo grew substantially as the kingdom of Kongo expanded and grew, and an ecclesiastical statement of the 1620s related that 4,500 baptisms were performed in the city and its immediate hinterland (presumably the valleys that surround it), which is consistent with an overall population of around 130,000 people. Of these, perhaps 30,000-45,000 lived in the nuclear city atop the mountain, while the remainder would have been distributed across smaller villages within the approximately 30-kilometre limit of its parish. Among the city's important buildings were some twelve churches, including São Salvador, as well as private chapels and oratories and an impressive two-story royal palace, the only such building in all of Kongo, according to visitor Giovanni Francesco da Roma (1648).^{[citation needed]}

The city was sacked several times during the civil wars that followed the Battle of Mbwila (or Ulanga) in 1665, and was abandoned in 1678. It was reoccupied in 1705 by Dona Beatriz Kimpa Vita's followers and restored as Kongo's capital by King Pedro IV of Kongo in 1709. It was never depopulated again though its population fluctuated substantially during the eighteenth and nineteenth century.