Artemisinin () and its semisynthetic derivatives are a group of drugs used in the treatment of malaria due to Plasmodium falciparum. It was discovered in 1972 by Tu Youyou, who shared the 2015 Nobel Prize in Physiology or Medicine for her discovery. Artemisinin-based combination therapies (ACTs) are now standard treatment worldwide for P. falciparum malaria as well as malaria due to other species of Plasmodium. Artemisinin is extracted from the plant Artemisia annua, sweet wormwood, a herb employed in Chinese traditional medicine. A precursor compound can be produced using a genetically engineered yeast, which is much more efficient than using the plant.

Artemisinin and its derivatives are all sesquiterpene lactones containing an unusual peroxide bridge. This endoperoxide 1,2,4-trioxane ring is responsible for their antimalarial properties. Few other natural compounds with such a peroxide bridge are known.

Artemisinin and its derivatives have been used for the treatment of malarial and parasitic worm (helminth) infections. Advantages of such treatments over other anti-parasitics include faster parasite elimination and broader efficacy across the parasite life-cycle; disadvantages include their low bioavailability, poor pharmacokinetic properties, and high cost. Moreover, use of the drug by itself as a monotherapy is explicitly discouraged by the World Health Organization, as there have been signs that malarial parasites are developing resistance to the drug. Combination therapies, featuring artemisinin or its derivatives alongside some other antimalarial drug, constitute the contemporary standard-of-care treatment regimen for malaria.