Mbuji-Mayi or Mbujimayi is a city and the capital of Kasai-Oriental Province in the south-central Democratic Republic of Congo. It is thought to b…Mbuji-Mayi or Mbujimayi is a city and the capital of Kasai-Oriental Province in the south-central Democratic Republic of Congo. It is thought to be the second largest city in the country, after the capital Kinshasa and ahead of Lubumbashi, Kisangani and Kananga, though its exact population is not known. Estimates range from a 2010 CIA World Factbook estimated population of 1,480,000 to as many as 3,500,000 estimated by the United Nations in 2008.