A Continuous Stirred-Tank Reactor (CSTR) is a type of reactor used extensively in chemical engineering and industrial processes for continuous chemical reactions. It consists of a well-mixed tank or vessel in which reactants are continuously added and products are continuously removed.

The defining feature of a CSTR is its continuous agitation, which ensures uniform mixing of the reactants throughout the vessel. This agitation can be achieved through mechanical stirring, pumps, or other mixing methods. As a result, the reaction occurs at a relatively uniform concentration throughout the reactor, maintaining a steady state.

CSTRs are known for their stability and versatility in handling various types of reactions. They're utilized in processes where a continuous flow of reactants is required, allowing for precise control over reaction parameters such as temperature, pressure, and concentrations. These reactors find applications in industries like pharmaceuticals, food processing, wastewater treatment, and petrochemicals, among others.