Introduction: Tinea pedis is a dermatophyte infection of human feet, especially between the fingers and soles of the feet. Tinea pedis is caused by a fungal infection of Trichophyton rubrum. Red onion is one of the spices that has been widely known by the community and used as a traditional medicine in the prevention of fungus. The objective of this research was to determine the antifungal activity of gel produced from an extract of red onion on T. rubrum. Materials and Methods: The gel was formulated with various concentration of red onion, FI with a concentration of extract (5%), F2 (7.5%). and F3 (12.5%). Each formula tested the physical characteristics and antifungal activity toward T. rubrum. The antifungal activity was determined by the agar well-diffusion method using Saboround Dextrose Agar plates. Furthermore, the antifungal activities were assessed by the presence or absence of inhibition zones after the plates were incubated at 28 degrees C for 7 days. Results: F3 has the greatest inhibitory power than F1 and F2 (P < 0.05). Then, F3 has the same inhibitory power as a positive control (P > 0.05). Discussion: All gel understudy at various concentrations of red onion was formulated in gel-exhibited antifungal activity. Antifungal activity of red onion occurred because it contained allicin. Therefore, the researchers can use these gels as a natural antifungal in the healing of tinea pedis caused by T. rubrum. Conclusion: The gel from an extract of red onion showed significant antifungal activity against T. rubrum.