Ringworm of Trichophyton tonsurans outbreak in a basic school in Valparaíso, Chile Background: Ringworm are skin and its annexes infections. Trichophyton tonsurans is an emergent anthropophilic fungus that might cause outbreaks. Aim: To describe a ringworm outbreak by T. tonsurans in an elementary school in Valparaíso, Chile. Methods: A descriptive study was run between June and August, 2018. Students and his closest relatives in contact with them who were clinically diagnosed with ringworm have been considered a case. Mycological studies of samples had been carried out through morphophysiology tests. Data are shown in numbers and percentages. Results: There were 18 cases, 16 kids (15 from kindergarten) and 2 adults. Attack rate was 68% in kindergarten. Nine cases were boys with average age of 6 years old. For 14 cases their nationality was Chilean and in 1 case Haitian. First case was a Chilean boy, and primary case was a Haitian boy. The most frequent location was face. Ten cases yielded positive cultures for T. tonsurans. Most of the patients needed terbinafine treatment after a therapeutic failure performed with clotrimazole. Conclusion: T. tonsurans outbreak ocurred mainly in kindergarten male. The most frequent location was face. Most of the patients needed terbinafine treatment after a therapeutic failure with clotrimazole.