Noted environmentalist Sunderlal Bahuguna died of COVID-19 at the All India Institute of Medical Sciences, Rishikesh on Friday.
Bahuguna breathed his last at 12.05 pm, AIIMS Director Ravikant said.
He is survived by his wife Vimla, two sons and a daughter.
The 94-year-old environmentalist known for his pioneering role in the Chipko movement was under treatment for COVID-19 at the hospital for over a week.
Admitted at the hospital on May 8 after testing positive for the infection, Bahuguna had been critical since Thursday night with his oxygen level dropping drastically.
He was on CPAP therapy in the ICU of the premier hospital.
Bahuguna was cremated with full state honours at the Poornanand Ghaat on the banks of the Ganga in Rishikesh.
His body was brought to the ghat wrapped in the national flag and was given a guard of honour by the Uttarakhand police.
Dehradun District Magistrate Ashish Kumar Shrivastava and SSP Yogendra Rawat laid wreaths on his body to pay their last respect to the environmentalist.
The funeral pyre was lit by his son Rajiv Nayan Bahuguna in the presence of his wife Vimla, daughter Madhu and other relatives.
Uttarakhand assembly speaker Prem Chand Aggrawal and Rishikesh mayor Anita Mamgai were also present.
Prime Minister Narendra Modi condoled Bahuguna's death, saying it is a "monumental loss" for the country.
"Passing away of Shri Sunderlal Bahuguna Ji is a monumental loss for our nation. He manifested our centuries-old ethos of living in harmony with nature. His simplicity and spirit of compassion will never be forgotten. My thoughts are with his family and many admirers. Om Shanti," the prime minister tweeted.
Chief Minister Tirath Singh Rawat condoled his death describing it as a big loss not just for Uttarakhand and India but for the entire world.
"It was he who made the Chipko movement a movement of the masses," Rawat said.
The void created by his passing away in the field of environment conservation can never be filled, the chief minister said.
He prayed for peace to the departed soul and strength to the bereaved family to bear the loss.
Born on January 9 in Tehri district, Bahuguna is considered the pioneer of the Chipko movement of the 1970s which he had launched along with dedicated environment conservationists like Gaura Devi to save forests.
Started by Bahuguna at the foothills of the Himalayas in 1973 in Uttarakhand, then a part of Uttar Pradesh, the Chipko movement was a forest conservation movement in India.
It later became a rallying point for many environmental movements all over the world.
Conferred with the Padmavibhushan and many other honours for his pioneering work in the field of environment protection, Bahuguna also led the protests against the construction of the Tehri dam.
He had observed an 84-day fast and got his head tonsured in protest against the project which displaced a huge population rendering them homeless.
He dug in his heels in protest against the project till the last minute. He had lost his own ancestral home due to the construction of the dam.
He also protested against the erstwhile Tehri royals which landed him in jail. He was also one of the most vocal critics of luxury tourism in the Himalayas and the construction of hotels which according to him did irreparable harm to the fragile Himalayan ecology.
He undertook several 'padyatras' to create awareness among people about conserving the Himalayan ecology and environment.
He was a big critic of the Rashtriya Swayamsevak Sangh.
Expressing his condolence at Bahuguna's death, another noted environmentalist Chandi Prasad Bhatt described him as a "brilliant social worker".
"His demise is painful for all of us," Bhatt said.