News organisations quoted a statement from the Central Clinical Hospital as saying he died after a long illness. No other details were given.
Though in power less than seven years, Mr Gorbachev unleashed a breathtaking series of changes, but they quickly overtook him and resulted in the collapse of the authoritarian Soviet state, the freeing of eastern European nations from Russian domination and the end of decades of East-West nuclear confrontation.
His power sapped by an attempted coup against him in August 1991, he spent his last months in office watching republic after republic declare independence until he resigned on Christmas Day 1991.
The Soviet Union wrote itself into oblivion a day later.
A quarter of a century after the collapse, Mr Gorbachev told the said he had not considered using widespread force to try to keep the USSR together because he feared chaos in a nuclear country.
“The country was loaded to the brim with weapons. And it would have immediately pushed the country into a civil war,” he said.
Many of the changes, including the Soviet break-up, bore no resemblance to the transformation he had envisioned when he became the Soviet leader in March 1985.
By the end of his rule he was powerless to halt the whirlwind he had sown, but he may have had a greater impact on the second half of the 20th century than any other political figure.
“I see myself as a man who started the reforms that were necessary for the country and for Europe and the world,” he said shortly after he left office.
“I am often asked, would I have started it all again if I had to repeat it? Yes, indeed. And with more persistence and determination,” he said.
Mr Gorbachev won the 1990 Nobel Peace Prize for his role in ending the Cold War and spent his later years collecting accolades and awards from all corners of the world, but he was widely despised at home.
Russians blamed him for the 1991 implosion of the Soviet Union — a once-fearsome superpower whose territory fractured into 15 separate nations. His former allies deserted him and made him a scapegoat for the country’s troubles.
The official news agency Tass reported that Mr Gorbachev will be buried next to his wife at Moscow’s Novodevichy cemetery.