Sinn Fein MLA for Fermanagh South Tyrone, Sean Lynch is stepping away from frontline politics.
The long-standing MLA was first elected to the Assembly back in 2011.
Having been sent to prison for 25 years in 1986, Mr Lynch was released 12 years later in 1998 under the terms of the Good Friday Agreement.
Elected in May, 2011, the ex-IRA man turned politician will be replaced by Aine Murphy, who is due to take up her role on Monday.
Paying tribute, Sinn Fein vice-president Michelle O'Neill thanked Mr Lynch for his years of dedicated service and activism as an Assembly member.
Ms O’Neill added: "For decades Sean has been a stalwart of republicanism, widely respected for his leadership skills as well as his on-the-ground activism.
"I want to thank Sean in particular for his tireless work for the people of Fermanagh and South Tyrone in the Assembly for many years.
"Sean may be leaving the Assembly but activists like him don't retire and I know he will continue to work for the people of Lisnaskea and the wider area as well as continuing to work to build the party and help his successor.
"I wish Sean and his family all the best for the future."
Meanwhile Aine Murphy said she is looking forward to representing the people of Fermanagh and South Tyrone alongside her party colleagues Jemma Dolan and Colm Gildernew as she prepares to join the Assembly tomorrow.
She said: "I want to pay tribute to Sean Lynch for his years of tireless service to the people of Lisnaskea and Fermanagh and South Tyrone and also for the support and guidance he has given me.
"I am determined to serve all the people of Fermanagh and South Tyrone and to make their voice heard in the Assembly chamber and on committees.
"There are many challenges and opportunities ahead of us and my priority will be to work alongside my colleagues to deliver a better health service, build more homes, create jobs and improve everyone's lives.
"This is an exciting time in politics across our island and I look forward to playing my part as an MLA to build a better, fairer, greener new and united Ireland for all."