"Madiba", as Mandela was affectionately called by his clan name by South Africans, passed away in the evening. The 95-year-old's death was announced late Thursday by South African President Jacob Zuma in a television address to the nation.
World leaders in unison paid tribute, including President Obama who said Mandela embodied the "promise of change for the better", BBC reported.
Obama said Mandela achieved more than what could be expected of any man.
"We have lost one of the most influential, courageous, and profoundly good human beings that any of us will share time with on this earth. He no longer belongs to us - he belongs to the ages," Obama said.
Obama, the first black president of the US, said he was one of the millions who drew inspiration from Mandela's life.
Obama has ordered flags at half-mast on all US public buildings until sunset on Dec 9 in honour of Mandela.
US First Lady Michelle Obama tweeted from the First Lady of the United States account: "We will forever draw strength and inspiration from Nelson Mandela's extraordinary example of moral courage, kindness, and humility."
British Prime Minister David Cameron said "a great light has gone out in the world".
Former British prime minister Tony Blair recalled on BBC World Service when Mandela visited Downing Street. "He would talk to the people on the door, to the people making the tea. He had an incredible way about him. It wasn't just what he did, it was the way that he did it."
Ela Gandhi, the granddaughter of Mahatma Gandhi, told BBC: "It is difficult for me to speak right now because I am so overcome with grief and emptiness... For me (Mandela) was really a wonderful hero and idol that I really felt that humanity should emulate, should follow."
Former England football captain David Beckham, who met Nelson Mandela in 2003, posted on Facebook: "My heart goes out to the people in South Africa and Mr Mandela's family. We have lost a true gentleman and a courageous human being. It was truly an honour to have known a man who had genuine love for so many people. Rest in peace."