Nelson Mandela Foundation
"We trust that this award will strengthen his commitment, as the leader of the most powerful nation in the world, to continue promoting peace and the eradication of poverty."
"It was an unexpected but inspired choice. In an increasingly challenging and volatile world, President Obama has given a sense of hope and optimism to millions around the world."
Afghan President Hamid Karzai
"We congratulate, wholeheartedly, President Obama on the award of this prestigious award. We recognize and commend President Obama's vision and leadership with a hope that peace and normalcy will return to Afghanistan and our region."
French President Nicolas Sarkozy
"It confirms, finally, America's return to the hearts of the people of the world."
Mikhail Gorbachev, the former Soviet leader and 1990 Nobel Peace Prize winner
"I am happy. What Obama did during his presidency is a big signal he gave hope. In these hard times, people who are capable of taking responsibility, who have a vision, commitment and political will, should be supported."
NATO Secretary-General Anders Fogh Rasmussen
"I warmly congratulate President Obama on winning the Nobel Peace Prize. President Obama has made extraordinary efforts to strengthen international diplomacy and cooperation between peoples."
Martti Ahtisaari, 2008 Nobel Peace Prize winner
"We do not yet have a peace in the Middle East ... this time it was very clear that they wanted to encourage Obama to move on these issues. This is a clear encouragement to do something on this issue. I wish him good luck."
Archbishop Desmond Tutu
"What wonderful recognition of someone who has already made such an impact on our planet with regards to the Muslim world, nuclear disarmament, climate change and, to some extent, the Middle East. He has reached out to the Arab world, including Iran, and North Korea.
In a way, it's an award coming near the beginning of the first term of office of a relatively young President that anticipates an even greater contribution towards making our world a safer place for all. It is an award that speaks to the promise of President Obama's message of hope."
Rebiya Kadeer, the Uighur leader who had been tipped for the prize
"I am very happy that he got it. Now he has to do something with the award. It raises expectations on him to stand up for oppressed nations."
Zabihullah Mujahid, a Taliban spokesman
"He has done nothing for peace in Afghanistan ... We condemn the award of the Nobel Peace Prize for Obama."
Mohamed ElBaradei, the director general of the International Atomic Energy Agency and 2005 winner of the Nobel Peace Prize
"I cannot think of anyone today more deserving of this honor ... President Obama has provided outstanding leadership on moving towards a world free of nuclear weapons."
Sami Abu Zuhri, a Hamas official
"Obama has a long way to go still and lots of work to do before he can deserve a reward. Obama only made promises and did not contribute any substance to world peace."
Saeb Erekat, a chief Palestinian peace negotiator
"We hope that he will be able to achieve peace in the Middle East and achieve Israeli withdrawal to 1967 borders and establish an independent Palestinian state on 1967 borders, with Jerusalem as its capital."
Morgan Tsvangirai, Zimbabwean Prime Minister, who was among those favored for this year's prize
"I wish to congratulate President Obama. I think he is a deserving candidate."
Obama's uncle, who is in Kogelo, Kenya
"It is humbling for us as a family, and we share in Barack's honor ... we congratulate him."
Ali Abkar Javanfekr, a media aide to Iranian President Mahmoud Ahmadinejad
"We are not upset, and we hope that by receiving this prize, he will start taking practical steps to remove injustice in the world. If he removes the veto from the United Nations Security Council, then it shows the prize was given correctly to him."
Shimon Peres, Israeli President
"Under your leadership, you have begun making peace a reality and making it a key issue on the agenda, which must be realized. From Jerusalem I express my confidence that the bells of understanding and dialogue between the nations will start ringing again."
José Manuel Barroso, the European Commission President
"A tribute to President Obama's commitment to the values of peace and progress of humanity. This award is an encouragement for engagement by all those who can contribute to bring about a safer world."