King, who is currently assistant coach at French Top 14 side Clermont Aubergnee, replaces Paul Grayson on the first team coaching staff, and will be handed the task of breathing new life into Saints’ attacking play.
Alan Dickens, who has been working as the temporary backs coach since Grayson’s departure, will be retained as part of the first team coaching set-up, while continuing his role as Academy manager.
Saints director of rugby Jim Mallinder said that King had been chosen after being ‘inundated with applications from coaches’.
The 37-year-old King has built up a reputation as one of the most exciting coaches in European rugby, and whle with Clermont he has helped the French club win the Top 14 for the first time in 2010, and reach the semi-finals of the 2012 Heineken Cup.
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This season they remain undefeated in a Heineken Cup pool which includes Leinster and Exeter, and currently lie second in the French league.
“I’m very excited about the prospect of joining Northampton Saints, which is one of the biggest clubs in Europe,” said King.
“In Jim Mallinder the Saints have a director of rugby that I respect greatly and a good, young team with plenty of talented English players.
“The club also has a great support base and I hope that I’ll be able to help bring success to Franklin’s Gardens.”
And he added: “I’ve had an amazing six years in France as a player and a coach.
“I always wanted to play in France and immerse myself in a different culture. I have done that and learned a great deal by working with great coaches like Vern Cotter, Joe Schmidt and Franck Azema.
“I feel that I am more knowledgeable about the sport and hopefully I can bring that to Northampton.
“I’m certainly looking forward to working with Jim, Dorian West and the other coaches at the Saints and believe that it is the right fit for me professionally and personally.
“It’s the right time for me to come home to England and to a club like the Saints, which has a very bright future.”
As a player King won everything there is to win in England, including two Heineken Cups and four league titles with Wasps, and Mallinder says that this knowledge, along with his more recent experience in France, will help the Saints take the next step in the club’s development.
“We have been inundated with applications from coaches over the past few weeks, but I believe that Alex is the right person to help us move forward as a group,” said Mallinder.
“As a player he was part of an excellent Wasps team, and as a coach he has helped Clermont Auvergne become one of the top clubs in Europe.
“He has built up a considerable amount of experience in a short space of time and is a coach who has some exciting ideas.
“I’m looking forward to Alex joining us in the summer and establishing himself at Franklin’s Gardens.”