Johannesburg (; ; also known as Jozi, Joburg and Egoli) is the largest city in South Africa and is one of the 50 largest urban areas in the world. It is the provincial largest city in Gauteng, which is the wealthiest province in South Africa. While Johannesburg is not one of South Africa's three capital cities, it is the seat of the Constitutional Court. The city is located in the mineral-rich Witwatersrand range of hills and is the centre of large-scale gold and diamond trade. 

In 2011, the population of the city of Johannesburg was 4,434,827, making it the largest city in South Africa. In the same year, the population of Greater Johannesburg Metropolitan Area was 7,860,781. Some view the area surrounding the city of Johannesburg yet more broadly than the metropolitan area, adding Ekurhuleni, West Rand and Lenasia; that larger area had a population of 8,434,292 in 2011. The land area of the municipal city () is large in comparison with those of other major cities, resulting in a moderate population density of . 

The city was established in 1886 following the discovery of gold on what had been a farm. The name is attributed to one or all of three men involved in the establishment of the city. In ten years, the population was 100,000 inhabitants.
Is the city built in a geographically flat area?
The city is located in the mineral-rich Witwatersrand range of hills