He played in the Pool stages of London Wasps' march to two Heineken Cup titles in 2004 and 2007 and won two Premiership titles and a Powergen Cup with the English club. In 2005 he was named as the Irish Rugby Union Players Associations (IRUPA) Players' Player of the Year.
"I'm happy with this decision I've come to following 14 years playing professional rugby and my body is telling me that it's 'my time' now. I've enjoyed my playing career massively and it wouldn't have been possible without all the people who've supported me along the way," said O'Connor.
"All the coaches and support staff I've worked with at both Connacht and Wasps have pushed and moulded me into the player and person that I am today. I'm especially grateful to Eric Elwood, who has believed in me from the outset and, during the last three years, has been a fantastic Head Coach.
" I hope to remain working in the rugby industry and keep an involvement with Connacht. I have a degree in Strength & Conditioning and wish to apply that knowledge, along with my first-hand experience, in a sports performance capacity."
O'Connor will continue to play to the end of the season before hanging up his boots. Connacht head coach Elwood was full of praise for his former team mate and player.
"It is with great regret that I have to bid farewell to a Connacht Legend on the announcement of his retirement at the end of the season. When Johnny pulled on that green shirt and took to the field, you knew that he was going to give you nothing less than 100%," said Elwood.
"People like Johnny are winners and I hope that he stays in the game in some capacity as I believe he has a lot to offer. "