President Michael D Higgins and former president Mary Robinson were among the guests at an event in Belfast to celebrate the life of trade unionist Inez McCormack.
Ms McCormack, who died in Derry two months ago, was the first female president of the Irish Congress of Trade Unions.
She was a personal friend of Hilary Clinton and an influential behind the scenes presence during the lengthy Good Friday Agreement negotiations.
In his address, President Higgins said Ms McCormack will be remembered as a great pioneer, who broke through so many challenges and barriers, and as someone who was a brave fighter.
He said she was a person of extraordinary generosity whose contribution to an inclusive citizenship and a better world has been immense.
Ms McCormack, who was 69 when she died, had been suffering from cancer.
She is survived by her husband, Vinnie, her daughter Anne and two grandchildren.