Naproxen, sold under the brand name Aleve among others, is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain, menstrual cramps, inflammatory diseases such as rheumatoid arthritis, gout and fever. It is taken orally. It is available in immediate and delayed release formulations. Onset of effects is within an hour and lasts for up to twelve hours.

Common side effects include dizziness, headache, bruising, allergic reactions, heartburn, and stomach pain. Severe side effects include an increased risk of heart disease, stroke, gastrointestinal bleeding, and stomach ulcers. The heart disease risk may be lower than with other NSAIDs. It is not recommended in people with kidney problems. Use is not recommended in the third trimester of pregnancy.

Naproxen is a nonselective COX inhibitor. As an NSAID, naproxen appears to exert its anti-inflammatory action by reducing the production of inflammatory mediators called prostaglandins. It is metabolized by the liver to inactive metabolites.

Naproxen was patented in 1967, and approved for medical use in the United States in 1976. In the United States it is available over the counter and as a generic medication. In 2020, it was the 91st most commonly prescribed medication in the United States, with more than 8 million prescriptions.