Colombo is located on the western coast of Sri Lanka, bordered by the Indian Ocean to the west. The Kelani River, one of Sri Lanka's major rivers, forms the northern boundary of the city before emptying into the sea. This coastal positioning has defined the city's climate, culture, and economy throughout its history.
Within the city limits, geography is a mix of land and water features. The most prominent inland body of water is Beira Lake, an extensive freshwater lake in the heart of the city that historically served defensive and transport purposes during the colonial era. The city's coastal edges feature both working port areas and public oceanfront greenspaces, most notably Galle Face Green.
The broader Colombo District transitions from highly urbanized coastal areas in the west to more suburban and semi-rural, verdant environments in the east and southeast. Natural resources in the immediate urban area are limited, but the region is rich in water resources, urban wetlands, and access to marine fisheries.