Coordinates: 28°37'N 77°14'E28.61°N 77.23°E Delhi, sometimes referred to as Dilli, is the second-largest metropolis in India and, with over 17.3 million residents, the sixth largest metropolis in the world by population. The metropolis lies within the federally-administered union territory known as the National Capital Territory (NCT) of Delhi. This article is about both the metropolis and territory of Delhi.

Located on the banks of the River Yamuna in the National Capital Territory of India, Delhi has been continuously inhabited since at least the 6th century BC, according to archaeological evidence. After the rise of the Delhi Sultanate, Delhi emerged as a major political, cultural and commercial city along the trade routes between northwest India and the Indo-Genetic plains. It is the site of many ancient and medieval monuments, archaeological sites and remains. In 1639, Mughal emperor Shahjahan built a new walled city in Delhi which served as the capital of the Mughal Empire from 1649 to 1857.

After the British East India Company gained control of much of India during the 18th and 19th centuries, Calcutta became the capital both under Company rule and under the British Raj, until George V announced in 1911 that it was to move back to Delhi. A new capital city, New Delhi, was built to the south of the old city during the 1920s. 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 migration of people from across the country, Delhi has grown to be a cosmopolitan metropolis. Its rapid development and urbanization, coupled with the relatively high average income of its population, has transformed Delhi. Today Delhi is a major cultural, political, and commercial center of India.