Mary Robinson has been appointed as UN Special Envoy for the troubled Great Lakes region of Africa.
The Tánaiste said Ms Robinson's "exceptional skills and experience as well as her global profile and reputation make her the ideal choice for this role".
All members of the UN Security Council supported her candidacy.
Her remit will be to implement a UN-supported agreement to end the cyclical violence in the central African region.
It is understood that Ms Robinson and her team will be based in Dublin and Bujumbura, the capital of Burundi.
Ms Robinson, 68, was President from 1990 to 1997. She was a UN high commissioner for human rights between 1997 and 2002.
Mr Gilmore also praised her work on poverty, hunger and climate change.
“I want to pay tribute to her ongoing work in this area and to wish her every success in her new position, where she can count on the full support of the Irish Government,” he added.