Voice by: Tom Kane
Born as Lord Montgomery Fiske, a British nobleman and world famous explorer and archaeologist, who became obsessed with monkeys. After training to become a master of Tai Sheng Pek Kwar (Monkey Kung Fu), he also spent his family's fortune on radical genetic procedures and experimental surgeries to replace his hands and feet with those of a monkey (in the season 2 episode "Partners," it is revealed that the procedures were performed by DNAmy, who developed a crush on Fist).
After tricking Kim into helping him steal a quartet of mystical idols, he used them to expose himself to "Mystical Monkey Power" and styled himself, Monkey Fist.
Unlike the other villains, he considers Ron Stoppable a worthy opponent rather than a clownish sidekick, since Ron and Rufus are the only other persons besides himself exposed to Mystical Monkey Power. although Ron considers Monkey Fist his arch-foe, in "Gorilla Fist" Monkey Fist claimed that he was an 'arch-bungler' at best. Ron once commented that he is the only one of their regular foes who regularly remembers Ron's name, a fact that Ron appreciates.
Besides his martial arts skills (greatly enhanced by the increased agility of his simian hands and feet), Monkey Fist commands an army of trained ninja monkeys. He is obsessed with increasing his power through various mystical artifacts and prophecies.
In "Oh No, Yono" his attempt to kidnap Ron's adopted sister, Hana, is thwarted and he is encased in stone. As of the finale episode, "Graduation," he is still encased in stone, thus making him the only villain on the series to have been "killed off," in a manner of speaking.