Kigali is located in the centre of Rwanda, at 1°57′S 30°4′E. Like the rest of Rwanda, it uses Central Africa Time and is two hours ahead of Coordinated Universal Time (UTC+02:00) throughout the year. The city is coterminous with the province of Kigali, one of the five provinces of Rwanda introduced in 2006 as part of a restructuring of local government in the country. The city has boundaries with the Northern, Eastern and Southern provinces. It is divided into three administrative districts—Nyarugenge in the south west, Kicukiro in the south east, and Gasabo, which occupies the northern half of the city’s territory. The built-up urban area covers about 70% of the municipal boundaries. Kigali lies in a region of rolling hills, with a series of valleys and ridges joined by steep slopes. It is situated between the two mountains of Mount Kigali and Mount Jali,^[22] both of which have elevations of more than 1,800 m (5,906 ft) above sea level, while the lowest areas of the city have an altitude of 1,300 m (4,265 ft). Geologically, Kigali is in a granitic and metasedimentary region, with lateritic soils on the hills and alluvial soils in the valleys.

The Nyabarongo River, part of the upper headwaters of the Nile, forms the western and southern borders of the administrative city of Kigali, although this river lies somewhat outside the built-up urban area. The largest river running through the city is the Nyabugogo River, which flows south from Lake Muhazi before flowing west between Mount Kigali and Mount Jali, and draining into the Nyabarongo. The Nyabugogo is fed by various smaller streams throughout the city, and its drainage basin contains most of Kigali’s territory, other than areas in the south which outflow directly to the Nyabarongo. The rivers are flanked by wetlands, which act as a water store and flood protection for the city, although these are under threat from agriculture and development.