Allyl methyl sulfide is an organosulfur compound with the chemical formula CH<sub>2</sub>=CHCH<sub>2</sub>SCH<sub>3</sub>. The molecule features two functional groups, an allyl (CH<sub>2</sub>=CHCH<sub>2</sub>) and a sulfide. It is a colourless liquid with a strong odor characteristic of alkyl sulfides. It is a metabolite of garlic, and "garlic breath" and/or "garlic body odor" is attributed to its presence. Consumption of polyphenol-containing foods has been shown to suppress the release of allyl methyl sulfide from the body.
It is prepared by the reaction of allyl chloride with sodium hydroxide and methanethiol.