The veteran BJP leader was admitted to SGPGIMS on July 4 following multiple ailments.
Born in Atrauli town of Aligarh district, Singh was Chief Minister of Uttar Pradesh twice -- June 1991 to December 1992 and September 1997 to November 1999.
He was at the helm of the affairs in Uttar Pradesh when the Babri masjid was demolished in 1992.
PM Narendra Modi condoled the death of Kalyan Singh.
“I am saddened beyond words. Kalyan Singh Ji…statesman, veteran administrator, grassroots level leader and great human. He leaves behind an indelible contribution towards the development of Uttar Pradesh. Spoke to his son Shri Rajveer Singh and expressed condolences. Om Shanti,” PM Modi tweeted.