The Liberian president, Ellen Johnson Sirleaf, and Leymah Gbowee, a social worker turned peace campaigner from the same country, will share the 10m kronor (£950,000) prize with Tawakkul Karman, a journalist and pro-democracy activist in Yemen who has been a leading figure in the protests against President Ali Abdullah Saleh since January.
The Nobel committee said the three had been chosen "for their non-violent struggle for the safety of women and for women's rights to full participation in peace-building work".
"We cannot achieve democracy and lasting peace in the world unless women obtain the same opportunities as men to influence developments at all levels of society," the committee said in a statement. They are the first women to be awarded the prize since 2004 when the committee honoured Wangari Muta Maathai, the Kenyan environmentalist who died last month, and bring the tally of female winners to 15, compared with 85 men.
Seen as a reformer and peacemaker in Liberia when she first took office, Sirleaf declared a zero-tolerance policy against corruption and has made education compulsory and free for all primary-age children. She is currently running for re-election, with a vote to be held on Tuesday.
Gbowee, 39, was instrumental in helping bring Liberia to peace in the early 2000s, leading a movement of women who dressed in white to protest against the use of rape and child soldiers in the war. During the 2003 peace talks, she and hundreds of women surrounded the hall where the discussions were being held, refusing to let delegates leave until they had signed the treaty. The committee said she had "mobilised and organised women across ethnic and religious dividing lines to bring an end to the long war in Liberia, and to ensure women's participation in elections".
Since 2004, Gbowee has served as a commissioner on Liberia's truth and reconciliation commission, and she is now executive director of theWomen in Peace and Security Network, an organisation that works with women in Liberia, Ivory Coast, Nigeria and Sierra Leone to promote peace, literacy and political involvement.
"In the most trying circumstances, both before and during the Arab spring, Tawakkul Karman has played a leading part in the struggle for women's rights and for democracy and peace in Yemen," the Nobel committee said of the third winner. Karman, 32, is a mother of three who in 2005 founded the group Women Journalists Without Chains.
She called her award "a victory for the Yemeni people, for the Yemeni revolution and all the Arab revolutions".
"This is a message that the era of Arab dictatorships is over. This is a message to this regime and all the despotic regimes that no voice can drown out the voice of freedom and dignity. This is a victory for the Arab spring in Tunis, Egypt, Libya, Syria and Yemen. Our peaceful revolution will continue until we topple Saleh and establish a civilian state."
The chairman of the Norwegian Nobel committee, Thorbjorn Jagland, told the Associated Press that Karman's award should be seen as a signal that both women and Islam had played an important part in this year's Arab uprisings. "The Arab spring cannot be successful without including the women in it," he said.
He said Karman belonged to a Muslim movement with links to the Muslim Brotherhood, an Islamist group "which in the west is perceived as a threat to democracy". He added: "I don't believe that. There are many signals that that kind of movement can be an important part of the solution."
Jagland told AP it was difficult to find a leader of the Arab spring revolts, especially among the many bloggers who played a role in energising the protests, and noted that Karman's work started before the Arab uprisings.
"It was not easy for us to pick one from Egypt or pick one from Tunisia, because there were so many, and we did not want to say that one was more important than the others." He noted that Karman had "started her activism long before the revolution took place in Tunisia and Egypt. She has been a very courageous woman in Yemen for quite a long time."
Sirleaf said the award "gives me a stronger commitment to work for reconciliation. Liberians should be proud".
Asked about the potential sensitivity of awarding an international prize days before the winner seeks re-election, Jagland said: "We cannot look to that domestic consideration. We have to look at Alfred Nobel's will, which says that the prize should go to the person that has done the most for peace in the world."