The Scarlets announced today they have agreed to release the 20-year-old winger with a year remaining on his contract, so he could sign a three-year deal with the East Midlands side.
Scarelts Chief Executive, Mark Davies said: "Everyone at the Scarlets will wish George the very best in his future career now that it is clear he will be playing his club rugby in Northampton for the next few years.
"Despite our desire to retain all our internationals within the region, we have to balance our available resource over the need to sustain a 50-deep player squad that can continue to compete during international periods.
"We are obviously massively disappointed to be losing a player of George's world-class quality and ability from Parc y Scarlets, however we appreciate the reality that the profile and success he has achieved in such a short space of time attracts huge attention and makes him a prized player for any club in Europe."
Christian Abt, George North's representative said: "Once we'd been informed by the Scarlets that a club outside the UK had made a significant approach, which the Scarlets had to consider, we focused on ways to keep George at the Scarlets, or within Wales.
"Given our initial intention to complete the existing contract, the Scarlets made the best offer they could for an extended agreement, but unfortunately, having taken into account every aspect involved in such an important decision, we were unable to agree terms.
"Following the recent weeks of much publicised debate, we are delighted to have reached an agreement with Northampton Saints who have made every effort to make what was a very difficult and emotional decision into a very sensible one, and George can now look forward and work hard throughout the remainder of his season with the Scarlets before his move to Northampton in the summer."
Allan Robson, Chief Executive of Northampton Saints said: "We are delighted to have reached an agreement with the Scarlets for George North to join us.
"He is an exceptional talent and one of the most formidable back-three attacking players in world rugby - withso much more to achieve in his rugby career at just 20 years old. We look forward with great anticipation to what he can bring to his performances with Northampton Saints next season."