Allyl methyl sulfide (AMS) is an organosulfur compound with the chemical formula CH₂=CHCH₂SCH₃. The molecule features two functional groups, an allyl (CH₂=CHCH₂) 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" is attributed to its presence. It is prepared by the reaction of allyl chloride with sodium hydroxide and methanethiol.

CH₂=CHCH₂Cl + NaOH(aq) + CH₃SH → CH₂=CHCH₂SCH₃ + NaCl + H2O