High shear mixers, also known as high shear reactors (HSRs), rotor-stator mixers, and high shear homogenizers, are used to emulsify, homogenize, disperse, grind and/or dissolve immiscible mixtures with components of the same or different phases. These machines have characteristics of high rotor tip speeds, high shear rates, localized energy dissipation rates, and higher power consumption than ordinary mixers.

Shearing forces mixing the components are generated by the relative motion of the rotating and stationary parts of the mixer. The rotating parts may be one or a set of impellers, paddles, or screws. The stationary parts, on the other hand, are the walls of the tank or chamber, and in some designs, baffles, and vanes.

High shear mixers are usually used in the manufacturing industry where different components or ingredients are mixed, such as food manufacturing, pharmaceuticals, cosmetics, plastics, and so forth. The principle of high shear mixers can also be seen in chemical and petrochemical plants where they are used to aid in the reaction process.