Saints have announced that Cobus Reinach will leave the club at the end of the season.
The South African scrum-half has long been linked with a move to Top 14 giants Montpellier.
And Reinach is now set to move on following the conclusion of his contract this summer.
The news is a blow to Saints as the 29-year-old was named supporters' and players' player of the year at the end of the previous campaign.
And he has been in fine form again this time round, having previously helped his country to World Cup glory in Japan.
“While we’re disappointed to lose a player of Cobus’ quality, we respect that in the final years of his professional career he’s made a decision with the long-term future of his family in mind,” said Saints boss Chris Boyd.
“Saints supporters love watching him play; he has provided them with plenty of memorable moments here at Franklin’s Gardens.
“I’ve been delighted with the form of Henry Taylor since his arrival at the start of the season, and with the emergence of Connor Tupai from our Academy set-up this year – plus getting Alex Mitchell back from injury in the coming weeks will feel like a new signing for us.
“Cobus is putting all his focus and energy into ensuring that Northampton have as much success as possible for the second half of the season, and we will wish him well after that.”