Express Mail Service, or EMS, is an international express postal service offered by members of the Universal Postal Union (UPU). The EMS Cooperative, which was created by UPU member countries in 1998, is responsible for promoting the harmonization and development of EMS services worldwide. As of 2015, EMS was offered by over 190 countries and territories around the world.

The EMS Cooperative uses an independent auditor to measure the express delivery performance of all international EMS operators. Based on this performance, EMS operators are awarded gold, silver, or bronze certificates, with the winners being recorded in the EMS Cooperative's Hall of Fame. These awards are intended to recognize and encourage high levels of performance and customer service in the EMS industry.