High-pressure water jets are used to clean surfaces and also to separate and remove surface layers. The mechanical and thermal load spectrum on the workpiece surfaces are low compared to other manufacturing technologies. Water jet cutting is generally applicable for machining a wide range of different materials with different component thicknesses. Waterjet or abrasive waterjet cutting is used especially for machining composite materials, some of whose individual components have widely differing material properties. After an introduction to the basic principles of material removal, different process variants are presented and the most important system components are introduced. The technology most frequently used in practice is water abrasive jet cutting. For this technology, a summary of the most important setting variables and quality characteristics of the machined workpiece is given at the end of the chapter.