This year's Nobel Peace Prize has been awarded jointly to three women - Liberian President Ellen Johnson Sirleaf, Liberian Leymah Gbowee and Tawakul Karman of Yemen.
The women had led the non-violent struggle for women's political rights, said the committee
They were recognised for their "non-violent struggle for the safety of women and for women's rights to full participation in peace-building work".
Mrs Sirleaf is Africa's first female elected head of state, Ms Gbowee a Liberian peace activist and Ms Karman is a leading figure in Yemen's pro-democracy movement.
Announcing the prize in Oslo, Nobel Committee chairman Thorbjorn Jagland said: "We cannot achieve democracy and lasting peace in the world unless women achieve the same opportunities as men to influence developments at all levels of society."
"It is the Norwegian Nobel Committee's hope that the prize... will help to bring an end to the suppression of women that still occurs in many countries, and to realise the great potential for democracy and peace that women can represent."
Mrs Karman heads the Yemeni organisation Women Journalists without Chains and has been jailed several times over her campaigns for press freedom and her opposition to the government of President Ali Abdullah Saleh.
She was recognised for playing a leading part in the struggle for women's rights in Yemen's pro-democracy uprisings "in the most trying circumstances".
'Iron Lady' Ms Karman, a mother of three, said she was dedicating her prize to "all the activists of the Arab Spring", the wave of unrest which has swept the Middle East and North Africa in the past year.
Nobel committee chair Thorbjorn Jagland announced the awards She is the first Arab women to win a Nobel Peace Prize.
Mr Jagland said the oppression of women was "the most important issue" in the Arab world and that awarding the prize was "giving the signal that if it [the Arab Spring] is to succeed with efforts to make democracy, it has to include women".
Ms Sirleaf, 72, had been widely predicted to be the winner of the 2011 prize.
She was elected in 2005, following the end of Liberia's 14-year civil war which left 250,000 people dead, caused thousands to flee abroad and financially ruined the country.
The US-educated economist and former finance minister, known as Liberia's "Iron Lady", pledged to fight corruption and bring "motherly sensitivity and emotion to the presidency" as a way of healing the wounds of war.
She is popular among women and the country's small elite, but disliked by more traditional male-dominated sections of society.
Mrs Sirleaf is standing for re-election next week, having previously said she would one hold the presidency for one term.
Ms Gbowee was a leading critic of the violence during the Liberian civil war, mobilising women across ethnic and religious lines in peace activism - in part through implementing a "sex strike" - and encouraging them to participate in elections.
"She has since worked to enhance the influence of women in West Africa during and after war," said the award citation.
The women will share the $1.5m (£1m) prize money.
The BBC's World Affairs correspondent Mike Wooldridge says that the Nobel Peace Prize originally recognised those who had already achieved peace, but that its scope has broadened in recent years to encourage those working towards peace and acknowledge work in progress.
The Nobel committee received a record 241 nominations for this year's prize - among the individuals and groups believed to have been put forward were the European Union, Facebook founder Mark Zuckerberg and key cyber dissidents in the Arab Spring movement.
Egyptian blogger and Google executive Wael Ghonim, who was jailed for his part in protests that led to the ousting of President Hosni Mubarak, congratulated Ms Karman on her "well-deserved win".
"Our real prize is for our countries to be more democratic and more respectful of human rights," he said on Twitter.
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