He's the first golfer to make a hole-in-one at any U.S. Open at Merion, which previously hosted four.
He used a 4-iron on the 213-yard, par-3 hole in Sunday's final round.
He made golfing history when his shot bounced out of the rough and rolled some 50 feet toward the pin before falling in the cup.
Stefani raised his arms and hopped around the tee in celebration. He shot a 1-under 69 in the final round.
He signed his glove and a scorecard to donate to the USGA Museum in Far Hills, N.J. He declined a request to give up the ball.