The Burnley fullback, 3 3, won 50 senior caps and represented his country at Euro 2012 and Euro 20-16.
The Dubliner said that he had made a decision to end his international career”with a heavy heart”.
“To represent my country has been a dream become a reality and the greatest honour I really could have had,” said Ward, who left his debut at 2011.
“To perform in a couple major championships has become the highlight and the nighttime time we beat Italy at the 20-16 Euros will live together with me for the remainder of my life.
“I have been quite pleased to have played a role in those achievements and that I believe this is a good time to move on.
“There really certainly are a great deal of good younger players and new talent coming through and that I wish all them, Mick [McCarthy] and the team all of the very best for future years.
Republic boss McCarthy, that signed Ward throughout his spell since Wolves manager, said:”He’s received 50 caps and he could retire being pleased with this achievement. I’m quite proud to have worked together with him because he was a excellent player for me personally and for Ireland.”
Ward made headlines last September when a recording of him discussing details of an altercation between then Republic helper manager Roy Keane and squad members Harry Arter and Jonathan Walters was forced public.