Pecos Bill is a mythical American cowboy, immortalized in numerous tall tales.

He was invented in the 20th century and is said to have lived during, and been a highly important figure in, the taming of the Western frontier. He embodied idealised cowboy virtues in a series of superhuman feats. He is credited as having been raised by coyotes near the Pecos River after falling from a wagon as a baby. On his return to humanity he invented the lasso, tamed and rode a cyclone, used a rattlesnake as a whip, could rope an entire herd at one go, used the entire Rio Grande to water his ranch, and performed other similar feats. He rode a horse called Widow-Maker and dated a girl called Slue-Foot Sue.

The stories were written by Edward O'Reilly in the Saga of Pecos Bill, published in 1923. He was a late addition to the "big man" idea of characters like Paul Bunyan or Iron John.

An animated short within Melody Time featured the character.