Northern Ireland defender Craig Cathcart has said his decision to retire from football at the age of 34 "was not an easy choice".
Cathcart made his Northern Ireland debut in 2010 and won 73 caps.
After his nine-year stay at Watford came to an end, he signed for KV Kortrijk in Belgium but ended his contract by mutual consent.
"I can no longer ignore the fact that my enthusiasm and motivation to play the game is not what it was," he said.
In an open letter to Northern Ireland supporters, Cathcart added that representing his country "was always an experience I treasured".