Chennai is situated on the southeastern coast of India, in the northeastern corner of Tamil Nadu. It lies on a flat coastal plain known as the Eastern Coastal Plains. The city is bisected by three primary water bodies: the Kosasthalaiyar River to the north, the Cooum River in the central region, and the Adyar River to the south. The historic Buckingham Canal, built during the British era, runs parallel to the coast, linking these rivers.
The city's eastern boundary is defined by the Bay of Bengal, featuring an extensive, sandy coastline. Inland, the geography comprises a mix of estuarine ecosystems, wetlands (such as the Pallikaranai marsh), and several lakes that act as crucial water catchments.
Notably, Chennai is one of the few global cities to house a national park within its metropolitan limits—the Guindy National Park, a scrub forest that serves as a vital green lung for the city and provides sanctuary to spotted deer, blackbucks, and various bird species.