Hassan, who had millions of fans in India and Pakistan, had been admitted to the Agha Khan Hospital in the southern port city of Karachi some days ago. He had been in a serious condition and was on ventilator.
"My father passed away at 12:22 PM after a long battle against different ailments," his son Arif Hassan said.
Hundreds of fans gathered at the hospital on learning of his death.
Hassan was born into a family of traditional musicians at Luna village in India's Rajasthan state in 1927. His family migrated to Pakistan at the time of Partition in 1947.
Hassan cut back on his performances in the late 1980s due to illness. (MORE)