A Bowie knife (pronounced  /ˈboʊ.iː/ BOH-ee or  /ˈbuːiː/ BOO-ee) is a pattern of fixed-blade fighting knife first popularized by Colonel James "Jim" Bowie in the early 19th Century. Since the first incarnation was created by James Black, the Bowie knife has come to incorporate several recognizable and characteristic design features, although its common use refers to any large sheath knife with a crossguard and a clip point.

The "Jim Bowie knife" first became famous due to Bowie's use of a large knife at a duel known as the Sandbar Fight. The knife pattern is still popular with collectors; in addition to various knife manufacturing companies there are hundreds of custom knife makers producing Bowies and variations.

The historical Bowie knife was not a single design, but was a series of knives improved several times by Jim Bowie over the years. The earliest such knife, made by Jesse Clifft at Rezin Bowie's request resembled Spanish hunting knives of the day, and differed little from a common butcher knife. The blade, as later described by Rezin Bowie, was 9.5 inches (24 cm) long, 0.25 inches (0.64 cm) thick and 1.5 inches (3.8 cm) wide. It was straight-backed, described by witnessess as "a large butcher knife", and having no clip point nor any hand guard, with a simple riveted wood scale handle.