Ludwig’s angina is a rapidly progressive and gangrenous cellulitis in the submandibular, sublingual spaces, and neck. It is characterized by an elevated tongue and laryngeal edema, resulting in airway compromise and, rarely, in sudden death. The most common cause is an odontogenic infection of a molar tooth. Infection can spread to the superior mediastinum and buccal area through anatomical structures. Herein, we report the sudden death of a 45-year-old male who was not diagnosed with Ludwig’s angina. He died in the emergency room 20 minutes after loss of consciousness. Intubation was impossible owing to severe laryngeal edema. The C-reactive protein level was 33.81 mg/dL. On autopsy, a diffuse light green abscess of the submandibular space was detected, along with severe edema of the epiglottis, aryepiglottic fold, and vocal cords. Subsequently, we confirmed that the airway obstruction was caused by Ludwig’s angina based on a literature review. In conclusion, this report emphasizes the need to identify the infection source and perform a detailed dissection according to the anatomical structure in the autopsy procedure for Ludwig’s angina.