Jai Singh II (3 November 1688 – 21 September 1743) was the Hindu Rajput ruler of the kingdom of Amber, he later founded the fortified city of Jaipur and made it his capital.
He was born at Amber, the capital of the Kachwahas.
He became ruler of Amber at the age of 11 after his father Maharaja Bishan Singh died on 31 December 1699.Initially, Jai Singh served as a Mughal vassal.
He was given title of Sawai by the Mughal Emperor, Aurangzeb in the year 1699, who had summoned him to Delhi, impressed by his wit.
On 21 April 1721, the Mughal emperor Muhammad Shah bestowed upon him the title of Saramad-i-Rajaha-i-Hind and on 2 June 1723, the emperor further bestowed him the titles of Raj Rajeshvar, Shri shantanu ji and Maharaja Sawai (which he personally sought from the Mughal emperor by means of various officials and gifts).
"Sawai" means one and a quarter times superior to his contemporaries.In the later part of his life, Jai Singh broke free from the Mughal hegemony, and to assert his sovereignty, performed the Ashvamedha sacrifice, an ancient rite that had been abandoned for several centuries.
He moved his kingdom's capital from Amber to the newly-established city of Jaipur in 1727, and performed two Ashvamedha sacrifices, once in 1734, and again in 1741.Jai Singh had a great interest in mathematics, architecture and astronomy.
He commissioned the Jantar Mantar observatories at multiple places in India, including his capital Jaipur.