John Thornton is the deuteragonist of Jack London's 1903 short adventure novel The Call of the Wild. He is Buck's final and ideal owner until he was killed by the Yeehats and Buck became a part of the wild.
He was portrayed by the late Clark Gable in the 1935 film, the late Charlton Heston in the 1972 film, the late Osamu Kobayashi and Mike Reynolds in the 1981 anime film, Rick Schroder in the 1993 film, the late Rutger Hauer in the 1996 film, and Harrison Ford in the upcoming 2020 film.
He is an experienced and wealthy gold hunter who lived in Alaska during the gold rush. When Hal, Charles and Mercedes try to cross the river to Dawson, Hal proceeds to beat up Buck. However, they have stumbled into Thornton's camp and he warns them about the thin ice. Hal continues to beat up Buck until Thornton beats him up and buys Buck from him. In spite of his warnings, the trio foolishly try to cross the river over the thin ice and they drown.
Ever since Thornton saved Buck's life, he felt affectionate for Thornton and loved him, even saving his life on occasions, such as defending him from a brute named Black Burton and rescuing him from a raging river. He also made friends with Thornton's two dogs named Skeet and Nig. One day, he comes across a gambler named Matthewson and he agrees to do a bet on Buck pulling 1,000 lbs. Buck eventually manages to win and Thornton earns his $1,600.
After the bet, Thornton hears about an abandoned mine and he and his friends go on a quest to find gold there. Meanwhile, Buck begins to hear strange howls from the wilderness and finds a lone wolf with its pack. Buck starts to become a part of the wild, while still being with Thornton. When Thornton and his friends finally find gold, they buy a team of sled dogs to head back to Dawson, but they are attacked and killed by a tribe of Yeehat Indians. Buck returns and avenges their deaths by killing the Yeehats. Thornton's death is what caused Buck to be a natural part of the wilderness and be free from humanity.
- John Thornton is very similar to Weedon Scott from London's other book White Fang. Both are wealthy gold hunters who rescue the canine protagonist from their abusive masters (Buck from Hal and White Fang from Beauty Smith). Both the dogs the men adopted only experienced friendship from their previous masters, while Thornton and Scott expressed love for the protagonists.
- In the 1996 adaptation, Thornton had a girlfriend named Maggie, who didn't exist in the book
- Thornton is the original sled master for Buck in some adaptations, while Francois and Perrault served as Buck's first sled masters in the book.
- He is renamed as Jack Thornton in the 1935 film.
- Thornton is based on a friend of Jack London.