In cooking, a chef's knife, also known as a cook's knife, is a cutting tool used in food preparation. The chef's knife was originally designed primarily to slice and disjoint large cuts of beef. Today it is the primary general-utility knife for most western cooks.

A chef's knife generally has a blade eight inches (20 centimeters) in length and 1+1⁄2 inches (3.8 cm) in width, although individual models range from 6 to 14 inches (15 to 36 centimetres) in length. There are two common types of blade shape in western chef's knives, French and German. German-style knives are more deeply and continuously curved along the whole cutting edge; the French style has an edge that is straighter until the end and then curves up to the tip.

Japanese kitchen knives have come under Western influence since the Meiji era, and many hybrid versions are available. The gyuto (牛刀 ぎゅうとう, gyūtō) "beef knife" is the Japanese term for a French (or Western) chef's knife. The gyuto were originally, and sometimes still called yo-boucho 洋包丁 meaning "Western Chefs Knife". The Santoku "three-virtue" knife is a style hybridized with traditional knives for more functionality. It is smaller, lighter and sharper with a different blade shape.

The Chinese chef's knife is completely different and resembles a cleaver. It is, however, functionally analogous to the Western chef's knife in that it's a general-purpose knife not designed for breaking bones.

A modern chef's knife is a multi-purpose knife designed to perform well at many differing kitchen tasks, rather than excelling at any one in particular. It can be used for mincing, slicing, and chopping vegetables, slicing meat, and disjointing large cuts.