Prednisone is a glucocorticoid medication mostly used to suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium due to cancer and adrenal insufficiency along with other steroids. It is taken by mouth.

Common side effects with long-term use include cataracts, bone loss, easy bruising, muscle weakness, and thrush. Other side effects include weight gain, swelling, high blood sugar, increased risk of infection, and psychosis. It is generally considered safe in pregnancy and low doses appear to be safe when breastfeeding. After prolonged use, prednisone needs to be stopped gradually.

Prednisone is a prodrug and must be converted to prednisolone by the liver before it becomes active. Prednisolone then binds to glucocorticoid receptors, activating them and triggering changes in gene expression.

Prednisone was patented in 1954 and approved for medical use in the United States in 1955. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2020, it was the 30th most commonly prescribed medication in the United States, with more than 19 million prescriptions.