Onychomycosis is a fungal infection of the nail, and the most common nail infection worldwide, causing discoloration and thickening of the nail plate. It is predominantly caused by dermatophytes. Clinical presentation is polymorphous. Diagnosis must be confirmed by mycological examination before initiating any therapy. Management is an ongoing challenge, often requiring several months' treatment, with a high risk of recurrence. Treatment must be adapted to clinical presentation and severity and to the patient's history and wishes. Debridement of all infected keratin is the first step, reducing fungal load. Systemic treatments are more effective than topical treatments, and combining the two increases the cure rate. Terbinafine is the drug of choice for dermatophyte onychomycosis, due to low drug interaction and good cost-effectiveness. Itraconazole and fluconazole are broad-spectrum antifungals that are effective against dermatophytes, yeasts, and some non-dermatophytic molds. Recurrence rates for onychomycosis are high. Prophylactic application of topicals and avoiding walking barefoot in public places may help prevent recurence.