Chennai district, formerly known as Madras district, is one of the 38 districts in the state of Tamil Nadu, India. It is the smallest and the most densely populated district in the state. The district is almost coterminous with the city of Chennai, which is administered by the Greater Chennai Corporation, except for Madipakkam-B / Madipakkam-II revenue village which is administered by Kovilambakkam rural village panchayat as Kovilabakkam panchayat wards 3,4 and 5 but is under Zone-14 (Puzhuthivakkam) of Greater Chennai Corporation for Disaster and Revenue Management purpose. It is surrounded by Tiruvallur district in the north and the west, Kanchipuram district in the south-west, Chenglpattu district in the south, and the Bay of Bengal in the east.
As of 2011, the district had a population of 67,48,026 with a sex-ratio of 989 females for every 1,000 males. Much of the district's population descended from its settlements in the 1st century CE to the Middle Ages, but the diversity has grown much since then. The district consists of two civic bodies, the megacity of Chennai and Kovilabakkam rural village panchayat wards 3, 4 and 5 (Madipakkam-B / Madipakkam-II revenue village colloquially known as Sunnambu Kolathur), which forms the core and the most notable portion of the much bigger Chennai metropolis, or officially, the Chennai Metropolitan Area. In 2018, the district's limits were expanded, aligning with that of the newly expanded Greater Chennai Corporation, which had annexed adjacent municipalities. It resulted in the area being increased from 175 square kilometres (68 sq mi) to 426 square kilometres (164 sq mi). The district is divided into three revenue divisions and ten taluks.