After a first peace deal rejected by the Colombian people, Santos's government and the Marxist FARC rebels renegotiated a new peace accord.
After a first peace deal rejected by the Colombian people, Santos's government and the Marxist FARC rebels renegotiated a new peace accord that was signed on November 24 to end a five-decade conflict that has killed more than 260,000 people, left 45,000 missing and forced nearly seven million to flee their homes.
"Something that was for many Colombians and for many Latin-Americans and for the world an impossible dream just a few years ago is now reality," Santos told reporters in the Norwegian capital on the eve of the prize ceremony.
The peace process had suffered a major setback on October 2 when Colombians narrowly rejected a first peace accord in a referendum.
While the "no" vote appeared to send Santos's chances of winning the Nobel up in smoke, the Norwegian Nobel Committee stunned world watchers five days later by awarding him the prize, arguing that Colombians had rejected the peace deal but not peace itself.
"It shows that peace is not made in one day," Berit Reiss-Andersen, deputy chairwoman of the Nobel committee, said on Friday.
The 65-year-old laureate called the prize a "gift from heaven" that gave a "tremendous push" to reach a new agreement with FARC.
"People in Colombia interpreted it as a mandate from the international community to persevere, to continue striving to achieve a peace agreement," Santos said.
"It encouraged me, it encouraged our negotiators, but particularly it encouraged the Colombian people to press" for a new deal, he said.
The peace deal, amended to include proposals from the opposition, calls for the rebels' disarmament and FARC's transformation into a political movement.
The Peace Prize will be presented early on Saturday afternoon at Oslo's City Hall at a ceremony attended by the royal family, members of the Norwegian government, representatives of victims of the conflict, and two high-profile former FARC hostages, Ingrid Betancourt and Clara Rojas.
The Nobel prize consists of a gold medal, a diploma and a cheque for eight million Swedish kronor (824,000 euros, $871,000), a sum Santos promised to donate to the victims of the war.
Later on Saturday, another ceremony will be held in Stockholm where the Nobel laureates in the sciences, economics and literature will be honoured -- a ceremony marked by the notable absence of this year's literature laureate, Bob Dylan.
The first songwriter to win the prestigious award, he has declined to attend the glittering ceremony due to "pre-existing commitments".
The no-show has created a stir in Sweden, where it has been perceived as a slight towards the Swedish Academy that awards the literature prize and the Nobel Foundation.
Announced as the winner on October 14, Dylan waited almost two weeks to publicly acknowledge the accolade, a silence one Academy member termed "impolite and arrogant".
Dylan did ultimately say he was honoured to win, but then informed the Academy in mid-November that he would not be travelling to Stockholm to accept his prize.
"A slap in the face," remarked editorialist Lena Mellin at one of Sweden's biggest dailies, Aftonbladet.
"Anyone who has ever received a prize, even if it's just for being the best neighbour in the apartment building, knows that the least one can do is go and accept it," she wrote.
On social media, opinions were mixed.
"If it were me, I would probably... collect a Nobel Prize and $900,000. But it's Bob, and that's part of what makes him Bob," wrote fan Evan Sarzin on the singer's Facebook page.
"He is 75, give him a break," argued another, Karen Lunebach.
"But what is Bob Dylan doing instead of going to the Nobel ceremony," asked daily Svenska Dagbladet on Friday, joking about his "pre-existing commitments" even though no concert was scheduled for Saturday.
The singer-songwriter has sent a thank-you speech to be read at the gala banquet at Stockholm's City Hall, attended by around 1,300 guests and the Swedish royal family.
And just before that, American rock star Patti Smith will sing Dylan's "A Hard Rain's A-Gonna Fall" during the formal prize ceremony at Stockholm's Concert Hall.
According to the Nobel Foundation, his prize should be presented to him in person sometime in 2017, either in Sweden or abroad.