The Pony Express was an American express mail service that used relays of horse-mounted riders between Missouri and California. It was operated by the Central Overland California and Pikes Peak Express Company.

Express mail is an expedited mail delivery service for which the customer pays a premium for faster delivery. Express mail is a service for domestic and international mail, and is in most nations governed by the country's own postal administration. Since 1999, the international express delivery services are governed by the EMS Cooperative.