Byrne, who is still on tour with the Lions in New Zealand, tied up a two-year deal with Watford-based Saracens over the weekend, after turning down a two-year contract offer from the IRFU.
A Leinster stalwart, hooker Byrne made 135 appearances for the province since making his debut back in 1992. The Aughrim man, who turns 34 in twelve days' time, has seen his Ireland career come on in leaps and bounds over the last three seasons, following Keith Wood's retirement from rugby.
Byrne, who was an unused replacement against Wales back in 1995, made his first Ireland start against Italy in 2002 and has garnered 38 caps in total in the green jersey.
Seen as an ideal replacement for veteran France hooker Raphael Ibanez, who flew the Sarries' coop with an early release from his contract, Byrne will come up against former provincial foes Ulster when Saracens visit Ravenhill for a Heineken Cup Pool 4 tie in early December.
Meanwhile, Connacht prop Peter Bracken has become the third Irish player to be recruited by Premiership champions Wasps this summer.
Wasps' forwards coach Craig Dowd said: "Peter is a good technician who gave some good props a rough ride last season.
"He is keen to succeed at the highest level, for both club and country, and moving to Wasps could give him that opportunity."
Ireland 'A' forward Bracken, admitted: "I'm very excited about moving to Wasps. Playing for such a successful team, and in the Premiership, is a huge challenge but one that I am looking forward to immensely.
"I'd like to thank all the staff and supporters at Galwegians and Connacht for their help and support in the past five years, and wish them all the best for the future."
Tullamore-born Bracken was originally heading to NEC Harlequins, his former club, but their relegationon on the last day of the 2004/05 season allowed Wasps to speak to the Connacht prop.