The 6-foot 6-inch guard had been highly sought after by the likes of Villanova, North Carolina and Kansas, but made his decision public via social media Thursday.
The 17-year-old Green is coming off a torn labrum sustained in his shoulder in July, but is expected to recover in time for his senior year at the IMG Academy in Florida.
He could replicate the path of fellow Australian Ben Simmons, a highly touted freshman at LSU who was picked No. 1 in the 2016 NBA draft -- though Green is deflecting similarities.
"The only comparison is we're Australian and we're playmakers," Green recently told Bleacher Report. "Some of the stuff he can do, I can't do, and the same thing goes the other way.
"The way I play, I don't really see too many comparisons. I feel like I'm my own self. I don't play like anyone else."
His coach at IMG Sean McAloon agrees. "He's not the next anybody. He's the first Josh Green," he told Bleacher Report.
Green's choice of Arizona will allow his parents, Cahla and Delmas Green, who both played pro basketball in Australia, to attend his games.
The family moved to Phoenix three years ago, when Green teamed with this year's No. 1 NBA draft pick Deandre Ayton in high school, providing 20.1 points per game.
Ayton played one season at Arizona, winning the Pac-12 conference and post-season tournament before entering the NBA draft, and his success may have steered Green in that direction.
"I appreciate my parents for letting us move over to America, but I'll always see myself as Australian," Green said in his announcement video posted on Twitter. He added: "I'll be proud to be part of the new wave of Australian success."
That new wave reportedly includes nearly 70 Australians playing NCAA Division I
basketball this season, and a further 10 on NBA rosters
. Aussies are also making waves in American football, particularly as punters.
The last five Ray Guy Award winners, given to college football's best punter, were Australian. They include Seattle Seahawks rookie sensation Michael Dickson, who joins five other Australians currently on NFL rosters.
'I will be vindicated'
Along with Green, Arizona lured five-star recruit Mannion in September. Both players cited the school's open style of play as an influence on their decisions.
Their commitments mark a positive step for Arizona's program, following a tumultuous season stained by an ongoing FBI corruption investigation reportedly involving the recruitment of Ayton.
Arizona coach Sean Miller sat out a game in February against Oregon after further reports, and lost the commitment of four-star recruit Shereef O'Neal, the son of NBA great Shaquille O'Neal.
Miller has denied any wrongdoing, saying in a statement he "will be vindicated.".
The university launched an independent investigation into the allegations last year, and supported Miller in a statement in March.
"At this time we have no reason to believe that Coach Miller violated NCAA rules or any laws regarding the allegation reported in the media," university president Robert Robbins said.
"We recognize that investigation is ongoing, and we will continue to be respectful and cooperative through its conclusion."