Chennai district , also and formerly known as Madras district, is a district in the state of Tamil Nadu, in India. It is the smallest of all the districts in the state, but has the highest human density. The district is a city district which means that it does not have a district headquarters. Most of the city region of Chennai comes under this district. As of 2011, the district had a population of 4,646,732 with a sex-ratio of 989 females for every 1,000 males.