This case report presents a maxillary third molar with a C-shaped canal system. This is the first known description of a maxillary third molar with C-shaped anatomy. This unique pulp chamber morphology was observed under the operating microscope. Root canal treatment consisted of cleaning and shaping combined with ultrasonic irrigation with sodium hypochlorite. A calcium hydroxide dressing was applied between appointments. Obturation of the root canal system was performed with warm vertical condensation. The complexity of this canal morphology requires the prudent clinician to perform strict measures to achieve satisfying results. Keywords: C-shaped, maxillary third molar, operating microscope, root canal morphology