George North says it has been an 'incredibly hard decision' for him to call time on his stay at Saints.
North will exit Franklin's Gardens in the summer of 2018 after opting to head back to Wales on a national dual contract.
He has made a total of 80 appearances for Saints to date, scoring 35 tries in the process.
The 25-year-old was a key part of the double-winning campaign, having joined Northampton from Scarlets in 2013.
But the Lions wing will now go back to Wales, having earned 38 of his 69 caps for his country while playing for Saints.
“This has been an incredibly hard decision,” North said.
“Saints have developed me as a player and stuck by me through thick and thin, so it is with a heavy heart that I have decided to move on.
"I love playing for Northampton Saints and am excited by the potential of the squad that is being assembled but, as a proud Welshman, I felt that now is the right time to move back home despite the compelling offer Saints made me.
“I feel very fortunate to have had the opportunity to be part of this great club for the last four years.
"I have loved every minute of my time here and I am excited to see what we can achieve this season.
"I will be putting everything I have into helping the squad fulfil our potential this year in the highly competitive Aviva Premiership, and I will sorely miss Franklin’s Gardens in the future.
“I would like to thank the squad, coaches, medical team, support staff and especially all of the supporters who have made my time at Northampton Saints so memorable.”