Mikhail Gorbachev, the former Soviet leader who brought the Cold War to a peaceful end, has died aged 91.
Mr Gorbachev, who took power in 1985, opened up the then-USSR to the world and introduced a set of reforms at home.
But he was unable to prevent the slow collapse of the Soviet Union, from which modern Russia emerged.
Tributes have been paid worldwide, with UN chief Antonio Guterres saying he “changed the course of history”.
“Mikhail Gorbachev was a one-of-a kind statesman,” UN Secretary General Mr Guterres wrote in a Twitter tribute. “The world has lost a towering global leader, committed multilateralist, and tireless advocate for peace.”
The hospital in Moscow where he died said he had been suffering from a long and serious illness.
In recent years his health has been in decline and he had been in and out of hospital. In June, international media reported that he had been admitted after suffering from a kidney ailment, though his cause of death has not been announced.
Russian President Vladimir Putin has expressed his deepest condolences following Mr Gorbachev’s death, his spokesman Dmitry Peskov told Russian news agency Interfax, according to Reuters.
US President Joe Biden called him a “rare leader” and praised Mr Gorbachev as a unique politician who had the “imagination to see that a different future was possible” amid the tensions of the Cold War.
European Union President Ursula von der Leyen praised him as a “trusted and respected leader” who “opened the way for a free Europe”.
“This legacy is one we will not forget,” she added.
UK Prime Minister Boris Johnson said he admired MR. Gorbachev’s courage and integrity, adding that “In a time of Putin’s aggression in Ukraine, his tireless commitment to opening up Soviet society remains an example to us all.”
Mr Gorbachev became general secretary of the Soviet Communist Party, and de facto leader of the country, in 1985.
At the time, he was 54 – the youngest member of the ruling council known as the Politburo, and was seen as a breath of fresh air after several ageing leaders. His predecessor, Konstantin Chernenko, had died aged 73 after just over a year in office.
Few leaders have had such a profound effect on the global order, but Mr Gorbachev didn’t come to power seeking to end the Soviet grip over eastern Europe. Rather, he hoped to revitalise its society.
The Soviet economy had been struggling for years to keep up with the US and his policy of Perestroika sought to introduce some market-like reforms to the state run system.
Internationally he reached arms control deals with the US, refused to intervene when eastern European nations rose up against their Communist rulers and ended the bloody Soviet war in Afghanistan that had raged since 1979.
Meanwhile, his policy of glasnost, or openness, allowed people to criticise the government in a way which had been previously unthinkable.
But it also unleashed nationalist sentiments in many regions of the country which eventually undermined the stability of the country and led to its collapse.
In 1991, after a shambolically organised coup by communist hardliners failed, Mr Gorbachev agreed to dissolve the Soviet Union and left office.