Former Taoiseach (Irish prime minister) John Bruton has died after a long illness.
In a statement, his family said the 76-year-old Fine Gael politician had died in the Mater Hospital in Dublin early on Tuesday.
"He was a good husband, a good father and a true patriot. We will miss him greatly," they said.
Mr Bruton served as taoiseach from 1994 to 1997.
He was instrumental in the evolving Northern Ireland peace process along with UK Prime Minister John Major, with whom he launched the Anglo-Irish Framework Document, external in 1995.
Sir John said he was "deeply saddened" to learn of Mr Bruton's death, describing him as a "formidable servant of the Irish nation and of peace".
"He was a brave and talented taoiseach who contributed mightily to the early days of the peace process," Sir John said.
"In testing circumstances, he put peace above political self-interest to progress the path towards the end of violence."
John Major (left) and John Bruton were heavily involved in the Northern Ireland peace process in the mid-1990s
Born in Dublin on 18 May 1947, Mr Bruton was elected to the Dáil (lower house of the Irish Parliament) to represent Meath in 1969.
As taoiseach he led a so-called "rainbow coalition" government of Fine Gael, Labour and Democratic Left but lost the 1997 general election to Bertie Ahern's Fianna Fáil party.
During his tenure as taoiseach he steered through a referendum that paved the way for the legalisation of divorce in Ireland.
He continued to lead Fine Gael until 2001 and later served as the EU ambassador to the United States.
In his tribute on Tuesday, present Fine Gael leader and Taoiseach Leo Varadkar described Mr Bruton as “a doer and a philosopher” who “made a particular effort to reach out to the unionist community”.
“He strongly opposed violence as a means to advance political objectives and believed in unity through consent" Mr Varadkar said.
"He advocated a new patriotism and opposed narrow nationalism.
"While these views are now held by the majority of people, that was not always the case.”
Mr Varadkar said Mr Bruton was one of the reasons he became involved in politics.
“Above all, I believe John Bruton possessed real dignity and imbued compassion and patriotism,” he added.
Irish President Michael D Higgins said he was privileged to work with Mr Bruton who he described as a "very energetic taoiseach" and a "deeply committed politician".
Mr Bruton brought a "particular sensitivity" and a "generous approach to inclusion" as he contributed to the Northern Ireland peace process, President Higgins added.
Former US President Bill Clinton (right) and John Bruton before a meeting in which they discussed the Northern Ireland peace process in December 1995
Mr Bruton's successor as taoiseach, Bertie Ahern, who led the Republic of Ireland during the period of the Good Friday Agreement, said Mr Bruton's involvement in Northern Ireland "was always genuine".
"My view of John is that he was a gentleman," Mr Ahern told RTÉ.
"He was a totally genuine person and always acted in the interests of the people of the country, of the people of need, and I wouldn't have a bad word to say about John Bruton."
European Parliament President Roberta Metsola said she was deeply saddened by the passing of Mr Burton.
The Ceann Comhairle (Speaker) of the Dáil, Seán Ó Fearghaíl, expressed his "deepest sympathies" to Mr Bruton's family on behalf of the Oireachtas (Irish parliament).
Members of the Northern Ireland Assembly also commented on Mr Bruton’s death during Tuesday morning’s sitting.
First Minister Michelle O’Neill and Deputy First Minister Emma Little-Pengelly extended their condolences to his family and friends.
"We've just been notified [he] has sadly passed away," Ms O'Neill, who is Sinn Féin vice-president, said.
"To his family and friends, we send them our condolences at this very sad time."
Assembly Speaker Edwin Poots said he would write to the Bruton family to express his condolences.
The King - when he was Prince of Wales - with John Bruton at a state banquet in Dublin Castle in May 1995
Northern Ireland Secretary Chris Heaton-Harris also said he was sorry to hear about the death of the former taoiseach.
"He positively impacted Anglo-Irish relations, and the Framework he agreed with John Major in 1995 was a crucial step in the road to the (Good Friday Agreement). My thoughts are with his family and friends," he shared on X.