Mr Hume was a key architect of Northern Ireland’s historic Good Friday peace agreement and was awarded the Nobel Prize for the decisive part he played in ending the Troubles.
The former Foyle MP, who had dementia and in recent years had lived in a care home in Derry, died in the early hours of Monday morning.
His funeral will take place in his native Derry on Wednesday morning in a ceremony limited in size due to coronavirus restrictions.
President Michael D Higgins said Mr Hume had transformed and remodelled politics in Ireland, while Taoiseach Micheál Martin said he was a “great hero and a true peacemaker”.
Former British prime minister Tony Blair hailed Mr Hume’s “epic” contribution to the peace process and former US president Bill Clinton insisted his legacy would live on.
Northern Ireland First Minister Arlene Foster and Deputy First Minister Michelle O’Neill also paid tribute.
Current SDLP leader Colum Eastwood, who represents the Foyle seat Mr Hume held for two decades, said the island had lost its most significant and consequential political figure of the 20th century.
As he signed a book of condolence in Derry on Monday, Mr Eastwood compared his political hero to the famous US civil rights leader.
“John Hume was our Martin Luther King,” he said.
“He was the greatest Irishman ever and he achieved something that no one could ever achieve before him: he ended the Anglo-Irish conflict, the conflict that had gone on for 800 years, and he gave my generation the opportunity to achieve our political goals peacefully and democratically, and that is an enormous legacy.”
Mr Hume, a former MEP for Northern Ireland, was a founding member of the party he went on to lead for 22 years.
He was a key figure in the civil rights campaigns of the late 1960s and also played a leading role in the formation of the credit union movement in his home city.
Throughout his political career he remained steadfast in his commitment to non-violence.
His participation in secret talks with then Sinn Féin president Gerry Adams in the late 1980s and early 1990s was a key catalyst for the nascent peace process.
The SDLP leader faced intense criticism, including some from within his own party, when his dialogue with Mr Adams became public in 1993.
Despite threats to his life, he persisted with his efforts to engage with the republican movement and to convince the IRA to end its campaign of violence.
On Monday, Mr Adams paid tribute to Mr Hume’s “bravery” and “persistence”.
“We have all lost a friend,” he said.
The highlight of Mr Hume’s career came in 1998 with the signing of the historic Good Friday accord which largely ended Northern Ireland’s 30-year sectarian conflict.
Along with Ulster Unionist Party leader David Trimble, Mr Hume was awarded the Nobel Peace Prize for his contribution to stopping the bloodshed.
In 2010, Mr Hume was named “Ireland’s Greatest” in a poll by RTÉ.
His death comes just six months after that of fellow Good Friday architect and long-time SDLP deputy leader Seamus Mallon.
British Prime Minister Boris Johnson said there would have been no Good Friday Agreement without Mr Hume.
“John Hume was quite simply a political giant,” he said.
“He stood proudly in the tradition that was totally opposed to violence and committed to pursuing his objectives by exclusively peaceful and democratic means.”
Mr Johnson added: “With his passing we have lost a great man who did so much to help bring an end to the Troubles and build a better future for all.
“His vision paved the way for the stability, positivity and dynamism of the Northern Ireland of today, and his passing is a powerful reminder of how far Northern Ireland has come.”
Taoiseach Micheál Martin described 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.
Mr Clinton said he and his wife Hillary had lost a friend who “fought his long war for peace in Northern Ireland”.
“His chosen weapon: an unshakeable commitment to non-violence, persistence, kindness and love,” he said.
“With his enduring sense of honour he kept marching on against all odds towards a brighter future for all the children of Northern Ireland.
“Through his faith in principled compromise, and his ability to see his adversaries as human beings, John helped forge the peace that has held to this day.”
President Michael D Higgins said Mr Hume had transformed and remodelled politics in Ireland.
“All of those who sought and worked for peace on our island of Ireland, and in the hearts of all, will have been deeply saddened by the passing of John Hume, Nobel Peace Laureate and statesman,” he said.
UK Labour Party leader Keir Starmer said: “Life across the island of Ireland is peaceful and more prosperous today because of his courage, vision and determination.”
In a statement, Mr Hume’s family said: “John was a husband, a father, a grandfather, a great-grandfather and a brother. He was very much loved, and his loss will be deeply felt by all his extended family.
“It seems particularly apt for these strange and fearful days to remember the phrase that gave hope to John and so many of us through dark times: we shall overcome.”
