With a central population of 17 million (2008) and an extended metropolitan population of more than 27 million, Delhi is the largest metropolis in India overtaking Mumbai and is one of the oldest continually inhabited cities in the world. It is also the world's most populous city within the municipal city limits. It is located on the banks of the River Yamuna in northern India and, as the National Capital Territory of Delhi (NCT), has the political status of a federally-administered Union Territory within the National Capital Region. In 1991, a constitutional amendment gave Delhi a special status among the Union Territories and its own legislative assembly with limited powers.

As of July 2007, the National Capital Territory of Delhi comprises nine districts, 27 tehsils, 59 census towns, 165 villages and three statutory towns – the Municipal Corporation of Delhi (MCD); the New Delhi Municipal Committee (NDMC); and the Delhi Cantonment Board (DCB).

Delhi has been the capital of several ancient Indian empires and a major city along the old trade routes between northwest India and the Indo-Gangetic Plains. It is the site of many ancient and medieval monuments, archaeological sites and remains. The Mughal emperor Shahjahan built the city and it served as the capital of the Mughal Empire from 1649 to 1857.

After the British Raj took control of India during the 19th century, Calcutta (now Kolkata) became the capital until George V announced in 1911 that it was to move back to Delhi. A new capital city, New Delhi, was built during the 1920s and it remains the area's administrative quarter. When India gained independence from British rule in 1947, New Delhi was declared its capital and seat of government. As such, New Delhi houses important offices of the federal government, including the Parliament of India.

Owing to the immigration of people from across the country, Delhi has grown to be a cosmopolitan city. Its rapid development and urbanisation, coupled with the relatively high average income of its population, has largely eclipsed socio-cultural traits that used to represent Delhi until a few years after independence. Today, Delhi is a major cultural, political, and commercial center of India.