Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may include lung abscess, acute respiratory distress syndrome, empyema, and parapneumonic effusion. Some include chemical induced inflammation of the lungs as a subtype, which occurs from acidic but non-infectious stomach contents entering the lungs.

Infection can be due to a variety of bacteria. Risk factors include decreased level of consciousness, problems with swallowing, alcoholism, tube feeding, and poor oral health. Diagnosis is typically based on the presenting history, symptoms, chest X-ray, and sputum culture. Differentiating from other types of pneumonia may be difficult.

Treatment is typically with antibiotics such as clindamycin, meropenem, ampicillin/sulbactam, or moxifloxacin. For those with only chemical pneumonitis, antibiotics are not typically required. Among people hospitalized with pneumonia, about 10% are due to aspiration. It occurs more often in older people, especially those in nursing homes. Both sexes are equally affected.