Russian news agencies announced his death on Tuesday, saying he had finally succumbed to "a serious and long illness."
Gorbachev was in power from 1985 to 1991. His career featured his helping douse the flames of the Cold War between his country and the United States.
It also witnessed his initiating economic and societal reforms across the Soviet Union that spun out of control, leading to the ruling system’s eventual collapse.
The changes won him praise in the West. It, however, also incurred him infamy among the Soviet Union’s supporters inside the country, who would find the collapse equal with the end of the country’s status as a “superpower” on the international stage.
While in power, Gorbachev also negotiated a historic nuclear arms pact with the United States then-president Ronald Reagan, which defused US-Soviet nuclear tensions. His helping emergence of the agreement also earned him the Nobel Peace Prize.
Russian President Vladimir Putin expressed his "deep sympathies" over Gorbachev's death. "In the morning [Putin] will send a telegram of condolences to his family and friends," Kremlin spokesman Dmitry Peskov told Russian news agencies.
Gorbachev will be buried in Moscow's Novodevichy Cemetery, Russia’s ITAR-TASS news agency reported.