The Nobel Peace Prize laureate's mild manners and gentle voice belied his conviction for his cause -- improving human rights in China.
"I feel that, in a dictatorship, if you want to be a person with dignity, if you want to be an honest person, you must fight for human rights and fight for freedom of speech," the writer and activist said in a 2007 interview. "Going to prison is part of that, and I have nothing to complain about."
He was granted medical parole in June after receiving his diagnosis in prison, but the Beijing government would not let him seek treatment abroad despite Liu's wishes and international pressure.
Many of his friends and supporters said at the time of his release that they feared the dissident was close to death
-- made a martyr by the Communist authorities.
"Whether it was gross negligence or political murder, they have committed an unprecedented crime as no other government of the world had ever seen a Nobel Peace Prize laureate die in its custody," said Hu Jia, a leading Chinese human rights activist, when Liu first left jail.
Hu has known Liu's wife, Liu Xia, for years and served prison terms for his own advocacy.
Liu was first jailed for his role in the 1989 pro-democracy movement after the bloody crackdown in Beijing's Tiananmen Square -- and later for petitioning for political reform and co-writing a paper on policy toward Taiwan that was at odds with the government stance.
His most recent conviction, in December 2009, stemmed from his co-authorship of Charter 08, a manifesto calling for political reform and human rights in China. He received a surprisingly harsh 11-year prison term for "inciting subversion of state power."
In October 2010, while serving his sentence at Jinzhou Prison, near Shenyang, Liu was named the winner of the Nobel Peace Prize for "his long and non-violent struggle for fundamental human rights in China."
Liu's wife tweeted at the time that, upon hearing the news from her during a prison visit, her husband started to cry and said: "This is for the martyrs of Tiananmen Square."
"His continued effort throughout these 20 years has not changed society, but he's influenced a lot of people," Liu Xia, who married Liu Xiaobo in 1996 while he was serving an earlier prison sentence, told CNN in 2009.
"More people share his views and more people are fearless -- I believe that's what makes his effort worthwhile."
An infuriated Beijing tried to block the news of Liu's Nobel win and boycott the award, insisting that he was a common criminal and the prize was nothing more than a Western plot against China.
Despite China's refusal to let Liu or a representative travel to accept the award, the Nobel ceremony organizers placed his citation and medal on an empty chair in a poignant event in December 2010 in Oslo, Norway.
Liu was born in December 1955 in northeastern China's Jilin Province. He moved to Beijing to pursue a graduate degree and eventually became a university lecturer in the capital.
Even during his teaching days, however, the bespectacled intellectual was viewed with suspicion by the authorities for his sharp rebuke of traditional ideologies and official doctrines.
"The passion he put into the way he was teaching -- even somebody like me, who had this kind of a language barrier on my first day, was able to appreciate how inspired and how excited the rest of the class was," recalled Ilaria Maria Sala, an Italian student of Liu's who stayed in touch with him over the years.
Armed with a doctoral degree in Chinese literature, Liu was a rising-star literary critic in the 1980s. He spent time in the United States and Europe as a visiting scholar, and turned his attention to the fight for democracy and human rights back home.
Having published numerous books on political and literary subjects overseas, Liu helped found the Chinese PEN Center, a literary and human rights organization. He later was on its board of directors in the 2000s.
'Forced to live in purgatory'
As Liu remained behind bars until recently, his wife -- an artist and a poet -- has paid a heavy price since his Nobel victory.
China put her under house arrest, rounded up Liu's supporters and froze diplomatic relations with Norway shortly after his peace prize win.
With her communication with the outside world almost completely cut by the government, Liu Xia has been suffering severe depression, according to friends, especially after authorities sentenced her brother to 11 years in prison over what supporters call trumped-up charges of business fraud.
"She didn't choose this life, but she'd been forced to live in purgatory," said Hu, the activist.
As for his own fate, Liu Xiaobo predicted that any Chinese Nobel Peace Prize winner would end up like Russian physicist and Soviet dissident Andrei Sakharov -- who received the prize in 1975.
"If China also has a dissident who becomes a Nobel Peace Prize laureate, it will be a big problem for the Chinese government," he told CNN in an interview in 2002 -- nearly eight years before receiving the award. "They can't imprison a Nobel laureate forever."