Delhi (/ˈdɛli/, Hindustani pronunciation: [d̪ɪlliː]Dilli; Devanāgarī: दिल्ली), officially the National Capital Territory of Delhi, is the capital territory of the Republic of India. Delhi is historically and culturally connected to both the Upper Doab of the Yamuna-Ganges river system and the Punjab region. It is bordered by Haryana on three sides and by Uttar Pradesh to the east. It is the second most populous city in India—about 1,484 square kilometres (573 sq mi). It has a population of about 25 million, making it the most populous city and second most populous urban agglomeration in India and 3rd largest urban area in the world. Such is the nature of urban expansion in Delhi that its growth has expanded beyond the NCT to incorporate towns in neighbouring states and at its largest extent can count a population of about 25 million residents as of 2014. After Mumbai, Delhi has the second-highest number of billionaires and millionaires among all cities in India.
Delhi has been continuously inhabited since the 6th century BCE. Through most of its history, Delhi has served as a capital of various kingdoms and empires. It has been captured, ransacked and rebuilt several times, particularly during the medieval period, and modern Delhi is a cluster of a number of cities spread across the metropolitan region.
Delhi and its urban region have been given the special status of National Capital Region (NCR) under the Constitution of India's 69th Amendment Act of 1991. The NCR includes the neighbouring cities of Faridabad, Gurgaon, Noida, Ghaziabad, Neharpar (Greater Faridabad), Greater Noida, Bahadurgarh, Sonepat, Panipat, Karnal, Rohtak, Bhiwani, Rewari, Baghpat, Meerut, Muzaffarnagar, Alwar, Bharatpur and other nearby towns. A union territory, the political administration of the NCT of Delhi today more closely resembles that of a state of India, with its own legislature, high court and an executive council of ministers headed by a Chief Minister. New Delhi is jointly administered by the federal government of India and the local government of Delhi, and is the capital of the NCT of Delhi.