Salil Shetty, who is currently director of the United Nations Millennium Campaign, will take up the role in June 2010.
He will be responsible for guiding Amnesty's worldwide sections and implementing the strategies, work plans and budgets of the organisation's governing body, the international executive committee. He will also be its chief spokesman and political adviser.
Shetty said: "I feel privileged to be given this amazing opportunity at a time when the world needs human rights for all more than ever before."
Peter Pack, chair of Amnesty's international executive committee, said: "We are thrilled that Salil will be joining us and leading Amnesty International as we renew our fight to end injustice – campaigning with those imprisoned because of their ideas, those on death row, those being tortured and those who have their rights denied because they live in poverty."
Shetty replaces Irene Khan, who will step down after eight years as secretary general on 31 December to join the board of the Charity Commission.