Austin Currie is being described as a "courageous leader".
The civil rights activist and former government minister died at his home in Derrymullen in County Kildare yesterday.
The 82-year-old, who co-founded the SDLP, later became a Fine Gael TD in Dublin West for 13 years.
President Michael D Higgins says Ireland has lost a 'dedicated, sincere and very committed politician'.
SDLP Leader Colum Eastwood says Austin Currie was an extremely brave public representative.
"I think he was the only person ever to hold Government office on both sides of the border.
"He was just a courageous leader, someone who suffered many attacks on his family home and against his family.
"He is someone who deserves tremendous respect for the change he made across this island."
