Ajoene (pronounced ah-hoe-ene) is a chemical compound available from garlic (Allium sativum). The name (and pronunciation) is derived from "ajo", the Spanish word for garlic.

Ajoene, an unsaturated disulfide, is formed from the bonding of three allicin molecules. Allicin is a sulfinyl compound that gives garlic its strong odor and flavor. The release of allicin (and the formation of ajoene) occurs after a garlic clove is crushed or finely chopped. Ajoene is also found in garlic extract. Ajoene is most stable and most abundant in macerate of garlic (chopped garlic in edible oil).

Scientists have recently found ajoene has many properties of interest to current medicine. It functions as an antioxidant, by inhibiting the release of superoxide. Ajoene also has antithrombotic (anti-clotting) properties, which helps prevent platelets in the blood from forming blood clots, potentially reducing the risk of heart disease and stroke in humans. Ajoene is also known to have effective broad-spectrum antimicrobial (antibacterial and antifungal) properties, helpful in preventing yeast infection (Candida albicans) and treating athlete's foot (tinea pedis), for example. Ajoene has even been shown effective in inhibiting tumor cell growth by targeting the microtubule cytoskeleton of such cells.