Acrylonitrile butadiene styrene, or ABS, (chemical formula ) is a common thermoplastic used to make light, rigid, moulded products such as pipes, golf club heads (used for its good shock absorbance ), enclosures and toys including LEGO Bricks. It is a copolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene . The proportions can vary from 15% to 35% acrylonitrile, 5% to 30% butadiene and 40% to 60% styrene. The result is a long chain of polybutadiene criss-crossed with shorter chains of poly(styrene-co-acrylonitrile). The nitrile groups from neighbouring chains, being polar, attract each other and bind the chains together, making ABS stronger than pure polystyrene. The styrene gives the plastic a shiny, impervious surface. The butadiene, a rubbery substance, provides resilience even at low temperatures. ABS can be used between -25°C and +60°C.

Production of 1 kg of ABS requires the equivalent of about 2 kg of oil for raw materials and energy.

Today, ABS is produced through a special process called grafting, rather than the copolymerization of acrylonitrile, styrene, and butadiene. In grafting, butadiene is polymerized first, then the cyanide and phenyl groups are added through a special chemical reaction.