"He no longer belongs to us. He belongs to the ages," Obama said in a somber appearance at the White House.
"I am one of the countless millions who drew inspiration from Nelson Mandela's life," he continued. "And like so many around the globe, I cannot fully imagine my own life without the example that Nelson Mandela set."
Mandela died earlier Thursday at 95. He had spent much of the year in and out of the hospital, and his illness prevented a meeting with Obama when the U.S. president visited South Africa this summer.
Still, the former South African president's legacy influenced nearly every aspect of Obama's trip. Obama, along with wife Michelle and daughters Malia and Sasha, made an emotional visit to Robben Island, standing quietly together in the tiny cell where Mandela spent 18 of his 27 years in prison. Obama also met privately with members of Mandela's family.
The president is likely to travel to South Africa for Mandela's funeral, though a trip has not yet been announced. Other former U.S. presidents and dignitaries are also likely to attend.
Obama's political rise has drawn inevitable comparisons to the South African leader. Both are Nobel Peace Prize winners and the first black men elected to lead their countries.
However, the two men met in person only once, a hastily arranged meeting in a Washington hotel room in 2005 when Obama was a U.S. senator. A photo of the meeting hangs in Obama's personal office at the White House, showing a smiling Mandela sitting on a chair, his legs outstretched, as the young senator reaches down to shake his hand. A copy of the photo also hung in Mandela's office in Johannesburg.
The two presidents did speak occasionally on the phone, including after the 2008 election, when Mandela called Obama to congratulate him on his victory. The U.S. president called Mandela in 2010 after the South African leader's young granddaughter was killed in a car accident. Obama also wrote the introduction to Mandela's memoir, "Conversations With Myself."
Mandela had already shaped Obama's political beliefs well before their first encounter. As a student at Occidental College in Los Angeles, Obama joined protests against the school's investments during South Africa's apartheid era. In 1981, Obama focused his first public political speech on the topic.
"It's happening an ocean away," Obama said, according to a retelling of the story in his memoir "Dreams From My Father." ''But it's a struggle that touches each and every one of us. Whether we know it or not. Whether we want it or not."
Satement from Former U.S. President Bill Clinton
Today the world has lost one of its most important leaders and one of its finest human beings. And Hillary, Chelsea and I have lost a true friend. History will remember Nelson Mandela as a champion for human dignity and freedom, for peace and reconciliation. We will remember him as a man of uncommon grace and compassion, for whom abandoning bitterness and embracing adversaries was not just a political strategy but a way of life. Our thoughts and prayers go out to Graça and his family and to the people of South Africa. All of us are living in a better world because of the life that Madiba lived. He proved that there is freedom in forgiving, that a big heart is better than a closed mind, and that life's real victories must be shared.
Statement from Former U.S. President Jimmy Carter:
Rosalynn and I are deeply saddened by the death of Nelson Mandela. The people of South Africa and human rights advocates around the world have lost a great leader. His passion for freedom and justice created new hope for generations of oppressed people worldwide, and because of him, South Africa is today one of the world's leading democracies. In recent years, I was gratified to be able to work with him through The Elders to encourage resolution of conflicts and advance social justice and human rights in many nations. We extend our heartfelt condolences to his family at this difficult time.
Statement by Former U.S. President George H.W. Bush 41:
Barbara and I mourn the passing of one of the greatest believers in freedom we have had the privilege to know. As President, I watched in wonder as Nelson Mandela had the remarkable capacity to forgive his jailers following 26 years of wrongful imprisonment -- setting a powerful example of redemption and grace for us all. He was a man of tremendous moral courage, who changed the course of history in his country. Barbara and I had great respect for President Mandela, and send our condolences to his family and countrymen.
Statement by Former U.S. President George W. Bush 43:
Laura and I join the people of South Africa and the world in celebrating the life of Nelson Rolihlahla Mandela. President Mandela was one of the great forces for freedom and equality of our time. He bore his burdens with dignity and grace, and our world is better off because of his example. This great man will be missed, but his contributions will live on forever. Laura and I send our heartfelt sympathy to President Mandela's family and to the citizens of the nation he loved.