The Hurricanes centre Matt Proctor will move to Britain after the 2019 Super Rugby season.
Proctor will join up with former Hurricanes coach Chris Boyd at Northampton.
Proctor made his Test debut for the All Blacks against Japan in November.
The 26 year old told the Saints website he's excited about the move.
"For a long time now, I have had the ambition of testing myself in the Northern Hemisphere and for so many reasons Northampton is a great fit for me.
"Not only will I have the opportunity to be coached again by Chris Boyd - the person I have worked with the most as a professional player - but I will also have the honour of joining a Club that is steeped in tradition and boasts a rich history of success.
"The Club and I share the same goals in wanting to achieve as much success as possible on the pitch, while also contributing to the wider rugby community off the field; so overall I am thrilled to be heading to Franklin's Gardens."
Boyd said: "Matt is exactly the calibre of player that we want to be bringing to Northampton - he's a world-class talent.
"I obviously know first-hand what he can do having worked with him back in New Zealand, and I am confident he can slot into our back-line next year alongside the quality players we already have at Saints.
"At 26, Matt is entering the peak years of his career and he had the desire for a new challenge on this side of the world. We feel that he can really fill his vast potential here in Northampton."
Saints are ninth in the Premiership, with Proctor their first new signing for the 2019-20 campaign.