"New Zealand will always be home, but Northampton presents a great opportunity for me to test myself in a new rugby environment, and reconnect with family there," Franks said in a statement.
Having never before plied his trade outside of New Zealand, Franks is relishing the prospect of northern hemisphere rugby.
"While I know I'll look back at the end of my time in New Zealand with an immense amount of pride, I still have a lot I want to achieve this year and some big goals to tick off before I leave," he added.
Franks made his Crusaders debut in 2009 and in June that year made his All Blacks debut against Italy aged 21 years and 186 days, the third youngest prop to play for the country.
He made his 100th Super Rugby appearance in the Crusaders match against the Otago Highlanders in 2015 and an All Blacks test centurion against Australia in Auckland last year.
"Owie is one of the most professional players I've had the privilege of coaching," All Blacks coach Steve Hanson said.
"His unbelievable commitment to his preparation, on-field and gym training, diet and his game is there for all to see, and inspires others.
"He has done this from the first time he made the All Blacks in 2009, has continued that throughout his whole career, and his achievement in reaching 106 Tests to date reflects that."
(Reporting by Hardik Vyas in Bengaluru; Editing by Andrew Cawthorne)
