Deputy First Minister Michelle O'Neill has hailed the late John Hume as "a huge figure in Irish politics for many years" who was "known the world over for his peacemaking efforts".
She said Mr Hume was "a leader who worked tirelessly for the community and his beloved Derry".
She added: "His work alongside Gerry Adams in the Hume-Adams talks were instrumental in creating the space for developing and progressing the peace process which led to the Good Friday Agreement."
Former Londonderry priest Denis Bradley, who witnessed Bloody Sunday and facilitated a secret channel between the IRA and the British government for over 20 years, recalled being a pupil of the then history teacher and he told how Mr Hume, who later went into politics, "had a big influence on me".
Mr Bradley said the former SDLP leader was "a good teacher" who was "passionate about education and politics".
Referring to Mr Hume's Derry roots, Mr Bradley added: "When it came to the peace process he had authenticity that very few other people had".
Austin Currie, founding member of the SDLP, said Mr Hume was "the greatest Irishman since Parnell" whose "place in Irish history is richly deserved".
"Despite the pressures on him, his family and his beloved Derry, he displayed great moral, physical and political courage," said Mr Currie.
"He never - not for one moment - departed from a complete insistence on the non-violent approach to our problems in Northern Ireland."
Irish President Michael D Higgins highlighted Mr Hume's "deep commitment" and "practical demonstration of tolerance and social justice, often times in the face of strong opposition and tangible threats to his person and his family, asserted the fundamental principles of democracy".
"He and those others who helped usher in a discourse that enabled a new era of civil rights and responsive government that few would have thought possible, have placed generations in their debt, have been a source of hope," Mr Higgins said.
"That his efforts were recognised through the awarding of the 1998 Nobel Peace Prize brought great joy not only to his people in Derry, his colleagues in politics, particularly in the SDLP, but to a wider global set of colleagues and fellow advocates for peace abroad who held him in the greatest esteem."
Irish PM Micheal Martin also paid tribute, describing Mr Hume as "a great hero and a true peacemaker".
"Throughout his long life he exhibited not just courage, but also fortitude, creativity and an utter conviction that democracy and human rights must define any modern society," he said.
"For over four decades, he was a passionate advocate for a generous, outward-looking and all-encompassing concept of nationalism and republicanism.
"For him the purpose of politics was to bring people together, not split them apart."
Tanaiste Leo Varadkar said Mr Hume was "one of Ireland's greatest ever sons".
He added: "He was a patriot, a peacemaker, a democrat, and a great, great Derryman."
The late poet Seamus Heaney's Twitter feed said that Mr Hume "made hope and history rhyme" adding: "He was the once in a lifetime oak tree who rose up with a longed-for tidal wave of justice. A patriot."
His predecessor Simon Coveney said: "John Hume has died. Ireland, all of us, should bow our heads in respect and thanks. What an extraordinary man, peacemaker, politician, leader, civil rights campaigner, family man, Derryman, inspiration. May he rest peacefully and his legacy live on."
Tributes were also paid by the chairman of the International Fund for Ireland, which the former SDLP leader had helped set up.
Paddy Harte described him as "one of the greatest peacemakers of our time" and a "true inspiration to us all".
"His passion paved the way for peace and reconciliation as we know it today, leaving those darkest days of the Troubles firmly in the past," he said.
"He leaves a legacy for peacemakers across the world and it is thanks to his influence that I hope we can continue our journey towards peace, knowing he has played an instrumental role in our work at the Fund."