Wales captain Dan Biggar will leave Northampton at the end of the 2022-23 season after five years with the Premiership club.
Biggar, 32, joined from Ospreys in 2018 and will depart when his current contract finishes.
The British and Irish Lions fly-half is unsure where he will move next.
"I have loved my time at Northampton Saints, a traditional rugby club which is full of great people from top to bottom," said Biggar.
The Wales fly-half is set to begin his new club career after the World Cup in France next year.
"I wish I could have played more for the club," added Biggar.
"I missed a few matches over the last few years due to my international commitments, but there isn't a better place to play rugby than Franklin's Gardens in front of an incredible group of supporters.
"I have made new friendships that will last forever, and it has been a pleasure to watch the young crop of academy guys mature and develop into first-team senior pros.
"There are too many brilliant people here to mention, but I hope we can all finish the season in spectacular fashion as we did last year, and go a couple of steps further."
Biggar singled out former director of rugby Chris Boyd, who left the club earlier this year, for special praise.
"I can't thank him enough for the way that he treated me, and gave me so many opportunities to represent this club," added Biggar.
"Saints will always be very special to me - and that includes the club's magnificent supporters, who have welcomed me in and supported me wholeheartedly through both the highs and lows. It has been a privilege."
Biggar, who has started all 68 games he has played for Northampton, has helped Saints to two top-four finishes in the Premiership in four seasons.
"Dan's quality as a player is obvious," said director of rugby Phil Dowson.
"He's a British and Irish Lion, a 100-cap Wales international, a leader who cares about the team.
"He loves pressure, and he loves to compete. His attitude is also exemplary.
"When he came to Saints back in 2018, we were a club in transition and there was a lot of expectation on him.
"He has been a major part of the rebuild of the team.
"We're now at a point where we believe we should be competing at the business end of major competitions, with a number of leaders within the squad who were just coming through when Dan arrived."