Robert L. Williams, often styled Robt. Williams, is an American painter, cartoonist, and founder of Juxtapoz Art & Culture Magazine. Williams was one of the group of artists who produced Zap Comix, along with other underground cartoonists, such as Robert Crumb, S. Clay Wilson, and Gilbert Shelton. His mix of California car culture, cinematic apocalypticism, and film noir helped to create a new genre of psychedelic imagery.

Zap Comix is an underground comix series which was originally part of the youth counterculture of the late 1960s. While a few small-circulation self-published satirical comic books had been printed prior to this, Zap became the model for the "comix" movement that snowballed after its release. The title itself published 17 issues over a period of 46 years.