The 25-year-old won relay silver at the Commonwealth Games in 2010 and represented Team GB at London 2012.
But he revealed last month that he was considering quitting after failing to make the 39-strong team for this summer’s Commonwealth Games in Glasgow.
Turner announced his decision on his Twitter account on Friday, saying: “Very excited today to announce my retirement from competitive swimming.”
Very excited today to announce my retirement from competitive swimming. It's been an unbelievable journey and one that I'm very proud of…
— Grant Turner (@MrGrantTurner) June 20, 2014