Hydroxychloroquine, sold under the brand name Plaquenil among others, is a medication used to prevent and treat malaria in areas where malaria remains sensitive to chloroquine. Other uses include treatment of rheumatoid arthritis, lupus, and porphyria cutanea tard. It is also used to prevent malaria infection in areas or regions where it is known that other medicines (eg, chloroquine) may not work. Hydroxychloroquine may also be used to treat coronavirus (COVID-19) in certain hospitalized patients.

Hydroxychloroquine is used in the treatment of arthritis to help relieve inflammation, swelling, stiffness, and joint pain and also to help control the symptoms of lupus erythematosus (lupus; SLE). A common brand name for hydroxychloroquine is Plaquenil®.