1,2,4-Trimethylbenzene is a colorless liquid with chemical formula C₉H₁₂. It is a flammable aromatic hydrocarbon with a strong odor. It occurs naturally in coal tar and petroleum (about 3%). It is nearly insoluble in water, but well soluble in ethanol, diethyl ether, and benzene.

Industrially it is isolated from the C9 aromatic hydrocarbon fraction during petroleum distillation. Approximately 40% of this fraction is 1,2,4-trimethylbenzene.

1,2,4-Trimethylbenzene dissolved in mineral oil is used as a liquid scintillator. It is also used as a sterilizing agent and in the manufacture of dyes, perfumes, and resins. Another major use is as a gasoline additive.