The school announced the decision Wednesday night.
Hansen, a redshirt freshman, completed all five of his passes for 70 yards in this year's spring game. He was competing with Trevor Knight, Baker Mayfield and Cody Thomas, who all have starting experience.
Oklahoma coach Bob Stoops said in a statement that he understood Hansen's desire to ''explore options that might provide him with more opportunity.'' Stoops specified that it will grant him a full release, with no restrictions.
Hansen said on Twitter that he was treated well by the coaches and he appreciated his time at the school.