City of Johannesburg, City of, metropolitan municipality (2011 pop. 4,434,827), Gauteng prov., NE South Africa. Johannesburg is the municipal seat; other communities include Soweto, Roodepoort, Alexandra, Orange Farm, Randburg, Sandton, Ivory Park, and Diepkloof. Mining and manufacturing are the principal industries. Johannesburg also is the capital of Gauteng and the financial and commercial center of South Africa.