Styrene monomer is an organic compound with the chemical formula C8H8. This derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell.

Styrene is one of the most important monomers produced by the chemical industry today. Styrene monomer is a basic building block of the plastics industry. The conventional method of producing styrene involves the inhalation of benzene with ethylene to produce ethylbenzene, followed by dehydrogenation of ethylbenzene to styrene. Styrene undergoes polymerization by all the common methods used in plastics technology to produce a wide variety of polymers and copolymers. Styrene is readily polymerized and copolymerized by both batch and continuous mass polymerization, emulsion, suspension and solution processes.

Styrene occurs naturally in small quantities in some plants and foods (cinnamon, coffee beans, and peanuts) and is also found in coal tar. Styrene is usually produced from dehydrogenation of ethyl-benzene. Also by combining toluene and methanol, and benzene and ethane, styrene can be produced. The presence of the vinyl group allows styrene to polymerize.