American chemist who, with Alan G. MacDiarmid (MacDiarmid, Alan G.) and Shirakawa Hideki, won the Nobel Prize for Chemistry in 2000 for their discovery that certain plastics can be chemically modified to conduct electricity almost as readily as metals.

After receiving a Ph.D. in physics from the University of California at Berkeley in 1961, Heeger taught and conducted research at the University of Pennsylvania until 1982, when he became professor at the University of California at Santa Barbara and director of its Institute for Polymers and Organic Solids. In 1990 Heeger founded the UNIAX Corporation to develop and manufacture light-emitting displays based on conducting polymers.

Heeger, MacDiarmid, and Shirakawa carried out their prizewinning work while studying polyacetylene, a polymer that was known to exist as a black powder. In 1977 the three men, collaborating at the University of Pennsylvania, exposed polyacetylene to iodine vapour. Their strategy was to introduce impurities into the polymer much as in the doping process used to tailor the conductive properties of semiconductors. Doping with iodine increased polyacetylene's electrical conductivity by a factor of 10 million, which made it as conductive as some metals. The finding led scientists to discover other conductive polymers and contributed to the emerging field of molecular electronics.