Prayagraj (; ˈpreɪəˌɡrædʒ,_'praɪə-); formerly Allahabad or Ilahabad or Prayag, is a metropolis in the Indian state of Uttar Pradesh. It is the administrative headquarters of the Prayagraj district—the most populous district in the state and 13th most populous district in India—and the Prayagraj division. The city is the judicial capital of Uttar Pradesh with the Allahabad High Court being the highest judicial body in the state. Prayagraj is the seventh most populous city in the state, thirteenth in Northern India and thirty-sixth in India, with an estimated population of 1.53 million in the city. In 2011, it was ranked the world's 40th fastest-growing city. Allahabad, in 2016, was also ranked the third most liveable urban agglomeration in the state (after Noida and Lucknow) and sixteenth in the country. Hindi is the most widely spoken language in the city.
Prayagraj lies close to Triveni Sangam, the "three-river confluence" of the Ganges, Yamuna and Sarasvati rivers. It plays a central role in Hindu scriptures. The city finds its earliest reference as one of the world's oldest known cities in Hindu texts and has been venerated as the holy city of Prayāga in the ancient Vedas. Prayagraj was also known as Kosambi in the late Vedic period, named by the Kuru rulers of Hastinapur, who developed it as their capital. Kosambi was one of the greatest cities in India from the late Vedic period until the end of the Maurya Empire, with occupation continuing until the Gupta Empire. Since then, the city has been a political, cultural and administrative centre of the Doab region.
Akbarnama mentions that the Mughal emperor Akbar founded a great city in Allahabad. ʽAbd al-Qadir Badayuni and Nizamuddin Ahmad mention that Akbar laid the foundations of an imperial city there which was called Ilahabas or Ilahabad. He was said to be impressed by its strategic location and built a fort there, later renaming it Ilahabas by 1584, which was changed to Allahabad by Shah Jahan. In the early 17th century, Allahabad was a provincial capital in the Mughal Empire under the reign of Jahangir.