The Tánaiste Brian Cowen has said Bertie Ahern will leave office with a great deal of dignity when he steps down on May 6.
Several cabinet ministers are expected to throw their hat in the ring for the Fianna Fáil leadership and the job of Taoiseach.
However, Mr Cowen is the odds-on favourite to secure the position after Mr Ahern personally identified him as his preferred successor.
Reacting to Mr Ahern's resignation announcement today, the Tánaiste said he and his colleagues wanted to thank the Taoiseach for his enormous contribution to politics in Ireland.
"He has been the outstanding politician of his era," Mr Cowen said.
Progressive Democrats leader Mary Harney also paid tribute to the Taoiseach today.
Ms Harney said she had worked with Bertie Ahern for 11 years on the basis of trust, personal respect, friendship and loyalty to the governments he led.
She said he, his family and his many friends and supporters can be very proud of his service to our country.