Fitzgerald, a test match starter for the Lions' tour of South Africa aged just 21, was limited to 34 caps for his country over the space of a decade by a series of injuries, most recently one to his neck suffered in last month's Pro12 final.
His club, Leinster, said that as a result of that incident, Fitzgerald had been advised to retire on medical grounds.
"It's been an amazing journey in which I got to experience the highs and lows that come with professional sport and I have learned a huge amount from each experience," Fitzgerald said in a statement.
"It's been an honour and a privilege to represent my province, my country and the British & Irish Lions. The support I got whilst playing for all three teams during the good times and the tough times is something I'll cherish and never forget."
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Fitzgerald, who made his Ireland debut as a teenager, was part of the squad that won the 2015 Six Nations title and was an ever present in the grand slam-winning side of 2009, Ireland's first clean sweep in 61 years.
A natural footballer who could play at centre and fullback, Fitzgerald scored his fourth international try in what would become his final international game in last October's World Cup quarter-final defeat to Argentina.
He also won three European Cups, a Challenge Cup and three Pro12 titles with his native province Leinster.
(Reporting by Padraic Halpin; Editing by John O'Brien)
