BOSTON — The Green are getting greener.

With aging stars Kevin Garnett and Paul Pierce on their way to the Brooklyn Nets and Doc Rivers already coaching the Los Angeles Clippers, the Boston Celtics hired 36-year-old Brad Stevens from Butler as their coach on Wednesday.

The move turns the tradition-laden franchise over to a mentor who led the Bulldogs to back-to-back NCAA title games but is younger than Garnett and wasn’t yet born when Bill Russell won his 11th NBA championship in 1969 (or even when John Havlicek added two more in the 1970s).

It’s the first time the Celtics have hired a college coach since Rick Pitino in 1997 and their first coach with no NBA experience of any kind since Alvin “Doggie” Julian, who was hired in 1948 and gave way to Red Auerbach two years later.

“Though he is young, I see Brad as a great leader who leads with impeccable character and a strong work ethic” Celtics general manager Danny Ainge said in a release. “His teams always play hard and execute on both ends of the court. Brad is a coach who has already enjoyed lots of success, and I look forward to working with him towards Banner 18.”

The Celtics gave Stevens a six-year deal worth about $22 million, according to a basketball official with knowledge of the deal who spoke on the condition of anonymity because the terms were not public. Ainge met with Stevens at his home in the Indianapolis area along with Celtics owners Wyc Grousbeck and Steve Pagliuca and worked out the deal Wednesday morning.

“It’s a wonderful opportunity with a historic franchise,” Butler President James M. Danko said at an on-campus news conference Wednesday night. “We have done everything we possibly can to keep him. Brad is a very bright, very articulate, and a wonderful, wonderful person who’s handled this as well as he’s handled everything else you’ve seen him do.”

Since taking Butler of the mid-major Horizon League to the national championship game in 2010 and again in ’11, Stevens had been courted by Illinois and UCLA, among others.

“But there are some brands in sports, and in the world of basketball the Celtics are one of those,” athletic director Barry Collier said, adding that Stevens’ contract ran through 2025. “That shows you the faith we had in Brad and the commitment we made to him. … I didn’t treat it as inevitable (that he would leave). I looked at it like every year Brad was our coach, it was another good year for Butler.”

Stevens spent seven years as a Butler assistant and the last six years as the head coach, compiling a career winning percentage of .772. He never won fewer than 22 games in a season, and the Bulldogs went 33-5 in 2009-10.

Stevens, who didn’t attend the news conference, takes over a team that is rebuilding just three seasons removed from an appearance in the NBA Finals; the Celtics won their unprecedented 17th championship in 2008. But with Garnett and Pierce showing signs of slowing down in this year’s playoffs, when Boston was eliminated by the New York Knicks in the first round, Ainge is trying to get younger.

He allowed Rivers to take over the Clippers, extracting a first-round draft choice in return. Amid last week’s NBA draft, the Celtics and Nets agreed to a deal that would send Garnett and Pierce to Brooklyn in exchange for a package of players along with three first-round draft picks.

In all, the Celtics have nine first-rounders in the next five years, along with a dynamic but temperamental point guard in Rajon Rondo and talented swingman Jeff Green.

Now, Stevens will be the one to work with those young players.

“Our family is thrilled for the opportunity given to us by the leadership of the Boston Celtics, but it is emotional to leave a place that we have called home for the past 13 years,” Stevens said in a release issued by the university. “We truly love Butler University and Indianapolis, and are very thankful to have had the opportunity to celebrate so many wonderful things together.”

At Butler, Stevens was 166-49 — the most wins for any Division I coach in the first six years of his career. In 2009-10, the Bulldogs posted the Horizon League’s first 18-0 conference record, a 25-game winning streak and an appearance in the NCAA title game, where they lost to Duke 61-59 when a last-second, half-court shot bounced off the backboard and rim and out.

“Brad has given his talent to our university with exceptional generosity, integrity, and humility,” Danko said, calling Stevens “a beloved member of our community.”

“We have done everything we can to keep Brad here at Butler; however, the Celtics team has offered Brad and his family a unique opportunity with which no university can compete.”