But Obama's ability to deliver on that hope is what troubles some observers.
"I couldn't believe it," says a Scandinavian diplomat whose wife called him Friday with the news. "I actually felt a little embarrassed for Obama, and for the Nobel committee. He [Obama] is going to have to accept this with the acknowledgement that he has still to earn it."
That sentiment was echoed in Britain, where the US president still enjoys high levels of approval. "He is a great, eloquent speaker and people admire that, but Tony Blair was also very eloquent, and many Britons are now cynical about what [Blair] ultimately achieved," says Dominic Dyer, executive director of the American European Institute in London.
Mairead Corrigan, a Belfast-born peace campaigner who was a joint winner of the 1976 Nobel Peace Prize for her work in Northern Ireland, said she was "very sad" to hear the news. "President Obama has yet to prove that he will move seriously on the Middle East, that he will end the war in Afghanistan and many other issues," she told the BBC.