Lord Fitt, one of the co-founders of the SDLP, was the dominant voice of nationalism in his hey-day.
Leading political figures have been given their reaction to his death.
MARK DURKAN, SDLP LEADER
I am deeply saddened by the passing of Gerry Fitt. I had spoken to him on the phone a few weeks ago and we had planned to meet when I was next in London.
Gerry Fitt was a key figure in the Civil Rights Movement and in the political life of the North for many years. As MP for West Belfast, he broke down the wall of indifference that British ministers and Westminster had previously shown towards Northern Ireland.
Mark Durkan described Fitt as "good company"
He was instrumental in founding the SDLP on the principles of non-violence, partnership and equality and in bringing about the Sunningdale Agreement, with its core features of power-sharing, a strong all-Ireland dimension and human rights.
The tragedy for him and everyone else was that Sunningdale was opposed and brought down by intransigent unionism and violent republicanism - the same people who now claim they are for the principles that were at its core.
While he was a great character and good company, Gerry Fitt should be remembered, above all, as someone who cared very deeply about the people.
PETER HAIN, NORTHERN IRELAND SECRETARY
Gerry Fitt was a courageous politician who fought against injustice in all its forms and demonstrated unrelenting opposition to violence from whatever source.
A true democrat, grounded in his working class roots, he always championed the rights of the most vulnerable in society and often at great personal cost to himself and family.
Peter Hain said Fitt was a "courageous politician"
He will be missed by many here as well as at Westminster where he continued, until very recently, to make a significant contribution in the life of parliament.
IAN PAISLEY, DEMOCRATIC UNIONIST LEADER
I am very sorry to hear of the passing of Gerry Fitt.
I offer my sincere sympathies to his family circle and his friends at this
BERTIE AHERN, IRISH PREMIER
I am deeply saddened to hear of the death of Gerry Fitt.
During a long and brave career in the wider labour movement and as a public representative he made a very significant contribution to constitutional politics and civil rights in Northern Ireland.
Through turbulent times at the height of the Troubles, he provided leadership to constitutional nationalists and an example to people of every creed.
He was a man who practised the message of moderation and tolerance that he courageously preached. He was often in the front line of the Troubles and he experienced violence at first hand from both sides of the divide in the north.
He was an excellent parliamentarian and a passionate speaker and he delivered many compelling speeches in both Houses of Parliament at Westminster.
He had a deep-seated commitment to equality and basic fair play, that stemmed from his strong socialist beliefs. Above all he abhorred sectarianism and violence.
In the ongoing quest for a peaceful settlement and constitutional politics in the north, history will record that he played his part by word, by deed and by example.
Gerry Fitt with his late wife Anne and their children, gave selfless public service to their community and to politics on these islands.
LORD KILCLOONEY, FORMER ULSTER UNIONIST DEPUTY LEADER
Gerry was a wonderful character. I remember him as a colleague at
Stormont when I was Home Affairs Minister.
Some politicians you cannot trust, but with Gerry you could always trust
He had a great sense of humour, very mischievous at times.
But he also made a huge contribution in the House of Lords to the debate on
Northern Ireland, because his understanding of the problems was so good.
SEAMUS MALLON, FORMER DEPUTY LEADER OF SDLP
Gerry was man who played a very central role at a time of great
change in Northern Ireland.
His efforts in Westminster, bringing the issues of justice in Northern
Ireland to the floor of the House, has so far been understated.
History will show that the way in which he brought the problems of Northern
Ireland to the immediate attention of parliament and a worldwide television
audience had a fundamental effect on what has happened since.
DANNY KENNEDY, ULSTER UNIONIST DEPUTY LEADER
He will always be respected and remembered for his consistent and resolute
opposition to the Provisional movement and their terrorist campaign, which
ultimately resulted in the loss of his Westminster seat.
As a parliamentarian many unionists would always remember him for his
opposition, in the House of Lords, to the changing of the RUC's name.
He was a passionate defender of the socially and economically disadvantaged
and made a lasting contribution to the political landscape in Northern
GERRY ADAMS, SINN FEIN PRESIDENT
The differences between Gerry Fitt and republicans were many and profound.
But this is not a time to revisit these.
I wish to express my sympathy to the extended Fitt family following the news of the death of Gerry Fitt.
JOHN HUME, FORMER SDLP LEADER
Gerry was a great human being, he was a very humorous man, but also a very committed man.
John Hume said Fitt had a great sense of humour
We always regretted when the break between himself and ourselves took place.
It came to our surprise and we regretted that very much, but in his early days we strongly supported what he did because he was very strongly in the Civil Rights Movement and strongly campaigning for Civil Rights.
He was the first MP from Northern Ireland to be allowed to even raise the Northern Ireland problem in the House of Commons.
Gerry's political legacy really was that he was a down to earth, working class, totally involved in trying to improve the living standards of his people.
LORD GLENTORAN, CONSERVATIVE SPOKESMAN ON NORTHERN IRELAND IN THE LORDS
Gerry Fitt was a giant of nationalist politics in Northern Ireland over the course of five decades.
Throughout his life he abhorred violence and was dedicated to pursuing his political objectives only by peaceful and democratic means.
He brought common sense, a deep personal knowledge, passion and wit to debates on Northern Ireland during his time at Stormont, in the House of Commons and latterly the Lords.
Above all, he will be remembered for his tremendous courage in the face of the most appalling intimidation by the IRA.
PAT RABBITTE, LEADER IRISH LABOUR PARTY
Gerry Fitt was one of the most important figures of the last 50 years in Irish political life.
In the 1960s, he put Labour politics on the map in Northern Ireland, through his activism at grassroots level and subsequent election to Belfast City Council, Stormont, and Westminster.
He was always a strong and passionate advocate of civil rights at a time when unionists failed to recognise or respond to these calls. He also demonstrated great personal courage in the face of worsening sectarianism.
Gerry Fitt's larger-than-life personality and his forthright, often blunt, approach won him enemies and friends alike.
Yet despite political differences with colleagues and opponents he remained committed to the politics of persuasion and to a peaceful, non-violent solution to the violence in the north.
ENDA KENNY, FINE GAEL LEADER
Gerry Fitt was a truly remarkable politician who made a huge contribution to the creation and development of democratic nationalism in Northern Ireland.
As a founder member and first leader of the SDLP he gave the nationalist population a vehicle to achieve civil rights and equality through politics.
Throughout his career, Gerry Fitt demonstrated huge courage, both in his steadfast opposition to all paramilitary violence and in exposing the criminality in which the provisional movement was engaged.
LEMBIT OPIK, LIBERAL DEMOCRAT SHADOW NORTHERN IRELAND SECRETARY
Lord Fitt was a testimony to courage and independence in the most divided year of Northern Irish Politics.
He was never afraid to say controversial things when necessary and was fearless when it came to challenging the status quo.