Manufacturing execution systems (MES) are computerized systems used in manufacturing to track and document the transformation of raw materials to finished goods. MES provides information that helps manufacturing decision-makers understand how current conditions on the plant floor can be optimized to improve production output. MES works as real-time monitoring system to enable the control of multiple elements of the production process (e.g. inputs, personnel, machines and support services).

MES may operate across multiple function areas, for example management of product definitions across the product life-cycle, resource scheduling, order execution and dispatch, production analysis and downtime management for overall equipment effectiveness (OEE), product quality, or materials track and trace. MES creates the "as-built" record, capturing the data, processes and outcomes of the manufacturing process. This can be especially important in regulated industries, such as food and beverage or pharmaceutical, where documentation and proof of processes, events and actions may be required.

The idea of MES might be seen as an intermediate step between an enterprise resource planning (ERP) system, and a supervisory control and data acquisition (SCADA) or process control system, although historically, exact boundaries have fluctuated. Industry groups such as Manufacturing Enterprise Solutions Association were created in the early 1990s to address the complexity, and advise on the execution of manufacturing execution systems.

MES solutions often interact with ERP systems to align the company's business operations with its production activities. This integration fosters information flow across departments enhancing efficiency and productivity. Organizations like MESA International provide guidance in implementing and advancing MES systems to help companies navigate the intricacies of manufacturing operations.

"Manufacturing Execution Systems [help] create flawless manufacturing processes and provide real-time feedback of requirement changes", and provide information at a single source. Other benefits from a successful MES implementation might include:

A wide variety of systems arose using collected data for a dedicated purpose. Further development of these systems during the 1990s introduced overlap in functionality. Then the Manufacturing Enterprise Solutions Association International (MESA) introduced some structure by defining 11 functions that set the scope of MES. In 2000, the ANSI/ISA-95 standard merged this model with the Purdue Reference Model (PRM).

A functional hierarchy was defined in which MES were situated at Level 3 between ERP at Level 4 and process control at Levels 0, 1, 2. With the publication of the third part of the standard in 2005, activities in Level 3 were divided over four main operations: production, quality, logistics and maintenance.

Between 2005 and 2013, additional or revised parts of the ANSI/ISA-95 standard defined the architecture of an MES into more detail, covering how to internally distribute functionality and what information to exchange internally as well as externally.^{[citation needed]}