Chennai has a diversified economic base with the recent growth being driven primarily by the auto, IT outsourcing and services industries. Chennai is a major manufacturing centre in India. Other important industries include petrochemicals, textiles and apparels. The Chennai Port and Ennore Port contribute greatly to its economic importance. The city also has its own stock exchange, the Madras Stock Exchange.

Chennai's service sector was traditionally dominated by finance and banking as many Indian and multinational banks have their administrative or business process bases in Chennai. Since the late 1990s, software development and business process outsourcing have have also emerged as major areas in the service sector. 

The IT Corridor on Old Mahabalipuram Road in the southeast of the city houses several technology parks. The largest of these is Tidel Park, built by TIDCO. One of the world's largest IT campus - the Mahindra World City is coming up in the outskirts of Chennai..

Chennai is the base for over forty percent of India's automotive industry. A good number of the automotive tier I suppliers in India are based in Chennai, mainly in the Ambattur-Padi industrial zone. Several automotive companies such as: Hyundai, Ford, Mitsubishi, BMW, TVS, Ashok Leyland, Caterpillar, Royal Enfield, TI Cycles and MRF have manufacturing plants in and around Chennai.

Chennai is an important centre for other service industries like advertising, healthcare and medical tourism. Chennai has perhaps the best medical facility of any city in India, and the city is also home to the world renowned Apollo Hospitals group. Chennai is home to the large Tamil entertainment (motion pictures, television, and recorded music) industry. Chennai is a major manufacturing centre with facilities ranging from small scale manufacturing to large scale industrial manufacturing. Chennai also has a large leather industry. Chennai has a biotech park called the TICEL Park adjoining the TIDEL Park and there is also a Bio-tech park for women at Siruseri.