President Michael D Higgins has led the tributes to Dan Rooney, the former US ambassador to Ireland who has died at the age of 84.
Mr Rooney was appointed to the role by Barack Obama in 2009 and served until he resigned from the post in 2012.
His death was confirmed by the Pittsburgh Steelers American football side.
In a statement, Mr Higgins said Mr Rooney was "deeply committed to Ireland and the Irish people."
He added that thanks to his contributions through the Ireland Funds "many projects promoting peace and reconciliation in Ireland were initiated."
Statement by President Michael D. Higgins on the death of Dan Rooney: pic.twitter.com/fDGxbqcHVU
— President of Ireland (@PresidentIRL) April 13, 2017
Mr Obama described Mr Rooney as a "great friend ... who represented the United States with dignity and grace on the world stage."
The US Embassy also issued a statement, saying Mr Rooney was "loved by all who met him, including everyone who worked with him at the U.S. Embassy in Dublin."
Mr Rooney was chairman of the Steelers club, which won four championships under his tenure.
— Pittsburgh Steelers (@steelers) April 13, 2017
Mr Rooney first became involved with the Steelers in 1955, later succeeding his father to become president of the franchise in 1975.
His son, Art, took over from him in 2003 and Dan Rooney became the club's chairman.
He was inducted into the Professional Football Hall of Fame in 2000.
Mr Rooney was a proud Irish-American and in addition to being named US Ambassador to Ireland by Mr Obama in 2009, he co-founded the Ireland Funds with Tony O'Reilly in 1976 which later merged with the American Irish Foundation to form the American Ireland Fund.
He served as Vice Chairman of the Fund.
John Fitzpatrick, Chairman of the Ireland Funds, said "Dan was an utter gentleman and utterly seflless."
He added that "the work of The Ireland Funds is his legacy and Ireland is a better place because of him. Thousands have benefitted from his care and concern."
Mr Rooney was born in Pittsburgh in 1932 and later married another Pittsburgh native, Patricia Regan, known as Peggy, and they had nine children.
He traces his Irish roots back to Newry in Co Down.
He also funded the annual Rooney prize for Irish literature which highlights the work of young Irish writers aged under 40.
