Labour TD Willie Penrose has announced he will not contest the next general election.
The Longford / Westmeath deputy was first elected to the Dáil in 1992, and has held his seat since.
He topped his constituency's poll in several elections up until 2011, but was only narrowly re-elected in 2016 - securing the fourth and final seat after a lengthy count process.
As well as serving as a TD, Deputy Penrose is also chairperson of Labour's parliamentary party, as well as their agriculture and rural affairs spokesperson.
The Chairperson of our Parliamentary Party Willie Penrose has decided not to put himself forward for the next election. Willie is a true Labour Party stalwart and has served the people of Longford-Westmeath in #Dáil for nearly 26 years. ?? pic.twitter.com/IfbGza2yfX
— The Labour Party (@labour) July 5, 2018
Party leader Brendan Howlin described Deputy Penrose as a "man of incredible integrity" and a "parliamentarian of the first order".
A selection convention to choose Labour's Longford / Westmeath candidate will take place this evening, with former Westmeath footballer Alan Mangan set to be selected as the candidate.
Deputy Penrose said: "I would not be stepping down if I didn't feel the candidate who is going to replace me was going to win the seat in Longford / Westmeath.
"We will work night and day to ensure the seat - which we won for the first time in 65 years in 1992 - is retained."
He added that his time as a TD has been a "great honour and great privilege".