o-Cymene, also known as 2-methyl-1-isopropylbenzene, is an aromatic organic compound with the chemical formula C₁₀H₁₄. It is classified as a monoterpene, specifically a member of the group known as cymenes, which are found in various essential oils. The name "o-Cymene" refers to the position of the two methyl groups on the benzene ring, with one on the ortho (o) position relative to the other. Other cymenes are p-cymene and m-cymene.

o-Cymene has been studied for various pharmacological properties, although it is not typically used as a pharmaceutical drug. Some reported biological effects include antioxidant and anti-inflammatory activity, as well as analgesic potential.

Cymene is also important in cannabis industry, as it alters how other aromatics smell and taste, Like most terpenes, cymene adds a woody, earthy, slightly menthol aspect to the flavor and smell of cannabis. While cymene is only present in small amounts in a few strains of cannabis, due to the entourage effect, its presence can significantly impact the type, length, and intensity of the “high” experienced.