One Smith commits to the All Blacks
That will take him through to the 2019 World Cup.
The 26-year-old, who helped steer the Highlanders to their inaugural Super Rugby title this year, has played 41 Tests since his international debut against Ireland in June 2012.
The All Blacks face a talent drain after this year's World Cup – with the likes of Richie McCaw, Dan Carter, Conrad Smith and Ma'a Nonu set to depart – and NZRU Chief Executive Steve Tew said retaining young talent such as Smith was important.
"With the signing of Aaron, together with Brodie [Retallick], Julian [Savea] and Dane [Coles], we now have a core group of key players committed long-term to the All Blacks and their Super teams, which is fantastic," he said.
"In the last few seasons he has developed into a key player for both the Highlanders and the All Blacks and is a world class player on top of his game."
The scrumhalf, Smith, also signed on with the Highlanders (Super Rugby) and Manawatu (NPC) teams.
He has played 78 games (including an amazing 60 consecutive matches) for the Highlanders and more than 40 matches for the Manawatu Turbos.
"I'm really excited and thankful for the commitment shown from the New Zealand Rugby Union, including the Highlanders and Manawatu Turbos," Smith said.
"Knowing I'm contracted for the next four years allows me to focus on my game and there are some exciting challenges ahead for the All Blacks which I hope to be part of.
"Dunedin is my home and I wouldn't want to play my Super Rugby anywhere else; the Highlanders brotherhood is something pretty special and I can't wait for next season."
Smith joins All Blacks teammates Julian Savea, Brodie Retallick and Dane Coles who announced four-year deals earlier this year, while Jerome Kaino and Wyatt Crockett are contracted through until 2018.
Players locked in to 2017 include Kieran Read, Sam Whitelock, Owen Franks, Cory Jane, Israel Dagg, Aaron Cruden, Ben Smith, Charlie Faumuina, Sam Cane, Steven Luatua, Malakai Fekitoa, Hikawera Elliot, Nepo Laulala, Codie Taylor, James Broadhurst, Tawera Kerr Barlow, Nehe Milner-Skudder, Waisake Naholo, Brad Weber, Charlie Ngatai and Ryan Crotty.
Sonny Bill Williams, Augustine Pulu, Beauden Barrett, Joe Moody, Lima Sopoaga, Luke Romano, Matt Todd, Victor Vito, George Moala, TJ Perenara, Dominic Bird, Patrick Tuipulotu and Andy Ellis are contracted through to the end of next year.
"It's outstanding news for Aaron and for the All Blacks," All Black Coach Steve Hansen added.
"With a number of senior players leaving at the end of this year, Aaron and other players will play a key role in the team as we face the exciting challenges coming up over that period, including the British and Irish Lions tour of New Zealand in 2017.
"We look forward to working with him."
Highlanders Head Coach Jamie Joseph commented: "Since I have known Aaron, he has blossomed into one of the best scrumhalves I have seen.
"In a sense he is redefining the halfback role by the way he plays, and you know players like that don't come along that often."
Highlanders' General Manager Roger Clark added: "Aaron's commitment to the Highlanders until 2019 is fantastic news. He is such an important member of the team and leadership group, and it's great to have that commitment from him to the team and the organisation."
Manawatu Rugby CEO John Knowles said: "Aaron remains a very important part of our community and we are delighted that he has recommitted to Manawatu. Every time he comes home he is out and about visiting schools and rugby clubs and inspiring the next generation of rugby players and we certainly appreciate his support."
