Osweiler, the first Arizona State quarterback to throw for more than 4,000 yards, completed 63.2 percent of his throws with 26 touchdowns and 13 interceptions this season. The tallest quarterback in the nation last year at 6 feet, 8 inches, Osweiler played in 25 career games, including 15 starts.
Osweiler, who is from Kalispell, Mont., led the Sun Devils to a 6-2 start, but then the team collapsed to finish 6-7 after losing to Boise State in the Maaco Bowl Las Vegas.
"It was an exceptionally difficult decision to make, but having spoken to my family and close friends, it became clear to me that this is the next path I must take to advance my personal and professional career," Osweiler said in a statement released by the school.
The school also released a statement from new coach Todd Graham, who replaced the fired Dennis Erickson.
"I met with Brock on several occasions and we discussed his future at length," the statement said. "Brock is doing what he believes is best for him and his family and we respect that. He will always have an open door to come back to at Arizona State University."
With Osweiler gone, the Sun Devils have little experience at quarterback. Rising sophomores Mike Bercovici, Osweiler's backup, and Taylor Kelly saw only mop-up duty this season. Redshirt freshman Michael Eubank is more athletic than Bercovici and Kelly and he was recruited by Graham when he coached at Pittsburgh.
Ted Miller covers Pac-12 football for ESPN.com.