A waterjet cutter is a tool capable of slicing into metal or other materials using a jet of water and abrasive at high velocity and pressure. It is often used during fabrication or manufacture of parts for machinery and other devices.

The cutter is commonly connected to a high-pressure water pump where the water is then ejected out of the nozzle, cutting through the material by bombarding it with the stream of high-speed water. Because the nature of the cutting stream can be easily modified, waterjets can be used to cut materials as diverse as fish sticks and titanium. Waterjet cuts are not typically limited by the thickness of the material, and are capable of cutting materials over twelve inches thick.

An important benefit of the waterjet cutter is the ability to cut material without interfering with the material's inherent structure as there is no "heat affected zone". Minimizing the effects of heat allows metals to be cut without harming or changing intrinsic properties. Waterjet cutters are also capable of producing rather intricate cuts in material.