Byrne won the United Rugby Championship four times and the Champions Cup during a 10-year spell with Leinster, where he made almost 200 appearances.
At international level, he has 22 caps for his country and has been part of teams that have won two Triple Crowns, one Six Nations title and a Six Nations grand slam.
The 30-year-old said the “brand of rugby” the Cherry and Whites now play, with a more expansive, attacking style, was one of the main factors in him joining.
“The brand of rugby is very exciting, hopefully I can add a little bit to that as well,” he said.
“It’s great to come into a team that wants to play that style of rugby with a bit of a balance as well, because ultimately winning is the most important thing, so hopefully we’re moving in the right direction.”
The appeal of playing at Kingsholm as well as in the top flight of English rugby union for the first time, was also another big factor.
Gloucester open their new season on Friday under the lights at home in the Premiership Rugby Cup before their first Prem Rugby match on 25 September away at Sale.
“Getting to play every second week here [at home] and the crowds they get, that is a huge reason I came here,” Byrne added.
“Obviously the Premiership itself and how competitive it is and each game home and away is a proper battle to win, I’m really looking forward to kicking off a competitive game this week [in the Premiership Rugby Cup] and then into the Premiership after that.”
