Jennings, who will captain Leinster tomorrow evening on the occasion of his 204th Leinster cap, will become the third most capped Leinster player when he leads the team out in the RDS against Zebre and is behind only Leo Cullen and Gordon D'Arcy.
Jennings made his debut with Leinster Rugby in September 2002 and has since gone on to win seven major trophies with Leinster including three Heineken Cups, three Celtic League titles and an Amlin Cup.
He also spent two seasons with the Leicester Tigers and won the Guinness Premiership, as it was known then, in 2007. In his time with the Tigers he won 60 caps in total scoring 12 tries.
Jennings was also capped 13 times by Ireland, scoring one try, and made his last appearance against Scotland in the 2012 6 Nations.
To date this season he has played six times for Leinster in the Guinness PRO12, scoring two tries, one against Connacht and another against Munster.
Speaking in the RDS Arena, Jennings said: "(Retiring) has been on my mind for a while to be honest. The last couple of weeks probably solidified my decision. It's been on my mind for a while. I've certainly taken my time to think about it, think about all the options, think about what I'm probably going to leave behind.
"There's a number of reasons. My body is battered and bruised, but thankfully it's not too bad. I've kind of been preparing myself over the last number of years with IRUPA through educational programmes and mentor programmes, and I've got a lot of assistance and a lot of help over the last few years to prepare myself for this. I'm very grateful that I'm going out on my terms.
"I'm very grateful that I've been part of such a great club, such a great team. It's been good times. But thankfully I'm confident I've made the right decision. I'm prepared, and I'm looking forward to the next stage of my life."
Matt O'Connor was alongside Jennings at the media briefing and had this to say about his time working with the St Mary's man: "It's been a pleasure to work with him over the last two season. I don't think think there's been a bigger contributor to the success of the organisation over the last few years than Jenno."
Guinness PRO12
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The Sweepstakes
Ballsbridge, Dublin 4, Ireland