Tunisia's National Dialogue Quartet won the prize “for its decisive contribution to the building of a pluralistic democracy in Tunisia in the wake of the Jasmine Revolution of 2011”.
Kaci Pullman Five, the new chair of the Norwegian Nobel Committee, said the prize was intended to inspire other countries in the region.
“It is a message both to the region and to the rest of the world,” she said. “Out of the Arab Spring countries, Tunisia is the only one where the development has proven so successful. We want to point to the fact that it is possible for Islamist and secular movements to work together.”
Houcine Abassi, the secretary general of the Tunisian General Labour Union, one of the Quartet's members, told Reuters he was “overwhelmed” by the decision.
“It's a message that dialogue can lead us on the right path," he said. "This prize is a message for our region to put down arms and sit and talk at the negotiation table.”
Anouar Moalla, a spokesman for the country's Truth and Dignity Commission, which is investigating crimes committed during the country's years of dictatorial rule, said that the announcement "gives us a lot of hope, this is something unbelievable.”
The award see the committee returning to a closer interpretation of the intentions of Alfred Nobel, after a decade of controversial choices, such as the 2009 prize to Barack Obama and the 2012 prize to the European Union.
“The broad national dialogue this quartet achieved is very close to the peace conferences outlined by Nobel in his will,” Kullman Five explained in an interview after the award.
"It is a very good prize that tries to get into the heart of the conflict in the Muslim world," said Øyvind Stenersen, a historian who runs the Nobeliana site, told AP. "But it was a bit bewildering. It was very unexpected."
UN spokesman Ahmad Fawzi congratulated the quartet, telling reporters in Geneva: "We need civil society to help us to move peace processes forward."
And European Union foreign policy chief Federica Mogherini said on Twitter that the award "shows the way out of the crises in the region: national unity and democracy".
The Quartet was formed in 2013 when the process of democratisation was in danger of collapsing because of widespread social unrest, "establishing an alternative, peaceful political process" at a time when Tunisia was on the brink of civil war, Kullmann Five said.
It is made up of the Tunisian General Labour Union, the Tunisian Confederation of Industry, Trade and Handicrafts, the Tunisian Human Rights League, and the Tunisian Order of Lawyers.
"More than anything, the prize is intended as an encouragement to the Tunisian people, who despite major challenges have laid the groundwork for a national fraternity which the Committee hopes will serve as an example to be followed by other countries," the Nobel panel said.
Since the Tunisia uprising that began in December 2010, the Arab world has been rocked by massive upheaval has toppled leaders in Egypt, Libya and Yemen and plunged Syria into a brutal civil war.
Tunisia has won praise for its political transition which has involved the adoption of a constitution in January 2014 and the holding of its first democratic elections at the end of the year.
But its fledgling democracy remains fragile. Tunisia has faced a spate of extremist attacks in 2015, including a massacre at a Tunis museum in March that killed 22 people, mostly tourists, and a mass killing at a beach resort last month that left 38 foreigners dead. Both were claimed by the Islamic State group.
It is the second time a Nobel peace honour has been bestowed in connection with the Arab Spring after Tawakkol Karman, an activist fighting Yemen's regime, shared the 2011 prize with Liberian President Ellen Johnson Sirleaf and Liberian "peace warrior" Leymah Gbowee for their struggle for women's
rights and empowerment.
rights and empowerment.
The prize is a gold medal, a diploma and a cheque for eight million Swedish kronor (around 860,000 euros/$950,000) to be shared by the laureates.
They will receive their prizes at a ceremony in Oslo on December 10, the anniversary of the 1896 death of prize creator Alfred Nobel, a Swedish philanthropist and scientist.
The Norwegian Nobel Committee did not specify in its release which representative of the four organisations was expected to come to the ceremony in Oslo on December 10 to collect the prize, with Kullman Five emphasising that the award was to the Quartet itself and not to its constituent organisations.
Last year, Pakistan's Malala Yousafzai, who was 17 at the time, became the youngest-ever winner of the Nobel Peace Prize in an award shared with India's Kailash Satyarthi for their struggle against the suppression of children and their right to education.