Former Cabinet Secretary TSR Subramanian died of natural causes on Monday, his family said. He was 79 years old.
Subramanian's son confirmed the news to IANS.
Subramanian was a 1961-batch officer of the Uttar Pradesh cadre in the Indian Administrative Services. He served as Cabinet Secretary from August 1996 to March 1998.
As the Cabinet Secretary, Subramanian was the senior-most government servant and headed the Cabinet Secretariat responsible for the administration of the Indian government.
The IAS Association said it was an "extremely" shocking and "sad news".
"He was the tallest amongst all and is a big loss for the IAS fraternity and the nation," the bureaucratic body tweeted.
"Deepest condolences to all family members. We hope and pray that your ideas and thoughts will continue to guide us," it said. His cremation will take place at the Lodhi Road crematorium at 5.30 p.m., the association said.
Subramaninan was part of a group of bureaucrats and diplomats on whose petition the Supreme Court in 2013 had rolled out key civil services reforms.
He worked hard to protect the bureaucracy from political interference.
Defence Minister Nirmala Sitharaman, Information and Broadcasting Minister Smriti Irani, Minister of State for Personnel Jitendra Singh also condoled his death.
"Saddened by the news. He was affable, full of ideas and energetic. In many a debate on TV channels, shared thoughts with him. Condolences to his family and his fraternity," Sitharaman said.
"Shocked to hear about the sad demise of TSR Subramanian ji. Had the good fortune of receiving his guidance on many a policy matters. My condolences to his loved ones. Om Shanti," Irani tweeted.
"Saddened by the news of the demise of former Cabinet Secretary ... My condolences to the entire @IASassociation fraternity and his family," Singh tweeted.