Orange Order grand secretary Drew Nelson has died aged 60 after a short illness.
Mr Nelson, from Dromore in Co Down, was described as a pragmatic and a "modernising force" for the loyal institution following his death.
He served as grand secretary for 16 years, during which he promoted gradual outreach by the staunchly Protestant and conservative organisation, engaging in meetings with the likes of the former Catholic primate Cardinal Sean Brady, former Irish president Mary McAleese and Taoiseach Enda Kenny.
The grand master of the Orange Order, Edward Stevenson paid tribute to Mr Nelson, saying the institution "has lost not only its heartbeat, but perhaps its greatest ever advocate.
“Whilst never compromising his beliefs as a principled and unashamed unionist, Drew’s pragmatism and strategic vision played a key role in the institution’s evolution as a major stakeholder in this province, and its ongoing community outreach.
“Indeed, his historic address to the Irish senate in 2012 broke new ground in this regard,” said Mr Stevenson.
The order's deputy grand master, Harold Henning, said Mr Nelson was the "modernising force" of the institution.
“No other Orangeman, of perhaps any generation, will ever match his motivation and drive to see the institution succeed and flourish,” he said.
“Drew was a trailblazer for Orangeism - the like of which we will never see again,” Mr Henning said.
Mr Nelson, a law graduate of Queen’s University Belfast, was a solicitor for 35 years, with his own practice in Dromore.
He was a part-time member of the Ulster Defence Regiment during the Troubles and also served as an Ulster Unionist Party (UUP) councillor from 1993 to 1997.
He stood unsuccessfully for Westminster in 1992 for the UUP against the SDLP’s Eddie McGrady in South Down, winning more than 25,000 votes. He left the UUP in 2004.
He was also a former chairman of Banbridge District Council.
Among the many tributes paid to Mr Nelson, the UUP Assembly member Danny Kennedy said he "led change in the order that saw its image and reputation improve significantly across the world".
The UUP leader Mike Nesbitt said Mr Nelson was a "modern, progressive form of Orangeman".
The DUP First Minister Arlene Foster said Mr Nelson was a "towering figure in the Orange Order, doing so much to contribute to its ideals and its reputation".
Jim Allister, leader of the Traditional Unionist Voice party, said Mr Nelson's "passion for a tradition which was frequently subject to unjust attack and caricature was evident to all who met him.
“Orangeism and the parading community generally have lost an intelligent and powerful advocate.”
DUP Assembly member William Humphrey, who is a member of the Orange lodge at Stormont, said the order had "lost an outstanding leader".