Trichophyton mentagrophytes is a species in the fungal genus Trichophyton. It is one of three common fungi which cause ringworm in companion animals. It is also the second-most commonly isolated fungus causing tinea infections in humans, and the most common or one of the most common fungi that cause zoonotic skin disease (i.e., transmission of mycotic skin disease from species to species). Trichophyton mentagrophytes is being frequently isolated from dogs, cats, rabbits, guinea pigs and other rodents, though at least some genetic variants possess the potential of human-to-human transmission, e.g. Type VII and Type VIII. Particular genetic variants of the fungus have distinct geographic ranges.