Mumbai is the commercial and entertainment centre of India, generating 5% of India's GDP and accounting for 25% of industrial output, 40% of maritime trade, and 70% of capital transactions to India's economy. Mumbai is home to important financial institutions such as the Reserve Bank of India, The Bombay Stock Exchange, The National Stock Exchange of India and the corporate headquarters of many Indian companies and numerous multinational corporations. The city also houses India's Hindi film and television industry, known as Bollywood. Mumbai's business opportunities, as well as its potential to offer a better standard of living, attract migrants from all over India and, in turn, make the city a potpourri of many communities and cultures.

The name Mumbai is an eponym, etymologically derived from Mumba or Maha-Amba—the name of the Hindu goddess Mumbadevi—and Aai, "mother" in Marathi. The former name Bombay had its origins in the 16th century when the Portuguese arrived in the area and called it by various names, which finally took the written form Bombaim, still common in current Portuguese use. After the British gained possession in the 17th century, it was anglicised to Bombay, although it was known as Mumbai or Mambai to Marathi and Gujarati-speakers, and as Bambai in Hindi, Persian and Urdu. It is sometimes still referred to by its older names, like Kakamuchee and Galajunkja. The name was officially changed to its Marathi pronunciation of Mumbai in 1996

A widespread explanation of the origin of the traditional English name Bombay holds that it was derived from a Portuguese name meaning "good bay". This is based on the fact that bom (masc.) is Portuguese for "good" whereas the English word "bay" is similar to the Portuguese baía (fem., bahia in old spelling). The normal Portuguese rendering of "good bay" would have been boa bahia rather than the grammatically incorrect bom bahia. However, it is possible to find the form baim (masc.) for "little bay" in sixteenth-century Portuguese.