Mumbai (/mʊmˈbaɪ/; also known as Bombay, the official name until 1995) is the capital city of the Indian state of Maharashtra. It is the most populous city in India with an estimated city population of 18.4 million. Along with the neighbouring regions of the Mumbai Metropolitan Region, it is second most populous metropolitan area in India, with a population of 21.3 million as of 2016. Mumbai lies on the Konkan on the west coast of India and has a deep natural harbour. In 2008, Mumbai was named an alpha world city. It is also the wealthiest city in India, and has the highest number of millionaires and billionaires among all cities in India.