Mumbai is India's largest city. Mumbai serves as an important economic hub of the country, contributing 10% of all factory employment, 40% of all income tax collections, 60% of all customs duty collections, 20% of all central excise tax collections, 40% of India's foreign trade and 40 billion Rupees (US$ 1 billion) in corporate taxes. Mumbai's per-capita income is Rs.48,954 which is almost three times the national average. Many of India's numerous conglomerates (including State Bank Of India, Tata Group, Godrej and Reliance), and four of the Fortune Global 500 companies are based in Mumbai. Many foreign banks and financial institutions also have branches in this area, the World Trade Centre (Mumbai) being the most prominent one. Up until the 1980s, Mumbai owed its prosperity largely to textile mills and the seaport, but the local economy has since been diversified to include engineering, diamond-polishing, healthcare and information technology. Mumbai is home to the Bhabha Atomic Research Center, and most of India's specialized, technical industries, having a modern industrial infrastructure and vast, skilled human resources. Rising venture capital firms, start-ups and established brands work in aerospace, optical engineering, medical research, computers and electronic equipment of all varieties, shipbuilding and salvaging, and renewable energy and power.

State and central government employees make up a large percentage of the city's workforce. Mumbai also has a large unskilled and semi-skilled labour population, who primarily earn their livelihood as hawkers, taxi drivers, mechanics and other such blue collar professions. The port and shipping industry, too, employs many residents, directly or indirectly. In Dharavi, in central Mumbai, there is an increasingly large recycling industry, processing recyclable waste from other parts of the city; the district has an estimated 15,000 single-room factories.

The media industry is another major employer in Mumbai. Most of India's major television and satellite networks, as well as its major publishing houses, are headquartered here. The centre of the Hindi movie industry, Bollywood produces the largest number of films per year in the world; and the name Bollywood is a portmanteau of Bombay and Hollywood. Marathi television and Marathi film industry are also based in Mumbai.

Along with the rest of India, Mumbai, its commercial capital, has witnessed an economic boom since the liberalization of 1991, the finance boom in the mid-nineties and the IT, export, services and BPO boom in this decade. The middle class in Mumbai is the segment most impacted by this boom and is the driver behind the consequent consumer boom. Upward mobility among Mumbaikars has led to a direct increase in consumer spending. Mumbai has been ranked 10th among the world's biggest centre of commerce in terms of financial flow in a survey compiled by Mastercard Worldwide.