Athlete's foot, known medically as tinea pedis, is a common skin infection of the feet caused by a fungus. Signs and symptoms often include itching, scaling, cracking and redness. In rare cases the skin may blister. Athlete's foot fungus may infect any part of the foot, but most often grows between the toes. The next most common area is the bottom of the foot. The same fungus may also affect the nails or the hands. It is a member of the group of diseases known as tinea.

Athlete's foot is caused by a number of different fungi, including species of Trichophyton, Epidermophyton, and Microsporum. The condition is typically acquired by coming into contact with infected skin, or fungus in the environment. Common places where the fungi can survive are around swimming pools and in locker rooms. They may also be spread from other animals. Usually diagnosis is made based on signs and symptoms; however, it can be confirmed either by culture or seeing hyphae using a microscope.

Athlete's foot is not limited to just athletes: it can be caused by going barefoot in public showers, letting toenails grow too long, wearing shoes that are too tight, and not changing socks daily. It can be treated with topical antifungal medications such as clotrimazole or, for persistent infections, using oral antifungal medications such as terbinafine. Topical creams are typically recommended to be used for four weeks. Keeping infected feet dry and wearing sandals also assists with treatment.

Athlete's foot was first medically described in 1908. Globally, athlete's foot affects about 15% of the population. Males are more often affected than females. It occurs most frequently in older children or younger adults. Historically it is believed to have been a rare condition that became more frequent in the 20th century due to the greater use of shoes, health clubs, war, and travel.