The Westgate Las Vegas Superbook lists Johnson as a 10/1 favorite to leave Royal Birkdale the champion golfer of the year.
Sunday's U.S. Open winner Brooks Koepka, who finished tied for 10th at St. Andrews in 2015, returns to The Open after missing last year's third major because of injury. He is available at 25/1.
Fourteen-time major winner and three-time Open champ Tiger Woods is not on the board.
The Westgate's complete sheet appears below: