A mail coach is a carriage specifically designed for carrying mail and a limited number of paying passengers. Mail coaches were historically used most extensively in Britain, and only for a very brief period of time, between the 1780s and the 1830s. Such coaches differed from stage coaches, which carried out journeys in stages with periodic rests; a mail coach was more expensive, but also much faster than a stage coach, making it a form of express delivery.

The British Post Office owned its mail coaches, and supplied guards for them. Contractors provided teams of four horses and drivers. Four passengers could sit inside a mail coach, with an additional three in front with the driver, while the guard stood on the back to guard the mail and parcels on the coach.

In many cases, a mail coach wouldn't even stop at official stops; instead, mail would be tossed down, with outgoing mail being hung on a post so that the guard could easily grab it and stow it away on the coach. This cut down on travel time significantly, although inns resented it because the lack of an official stop cut down on potential income from hungry or weary passengers.

Traveling by the mail coach would have been fast, but often uncomfortable. While the coaches were sturdy and padded, they often traveled on atrocious roads, subjecting passengers to extreme bumping, and they also ran through bad weather conditions, without heed to passenger comfort. However, the speed and convenience were often worth it, in the eyes of passengers in a hurry.

Prior to the introduction of the mail coach, mail was carried by riders who traveled from stop to stop. These couriers were often vulnerable to robbery, because they had limited self-defense options. While the concept of the mail coach was resisted at first, ultimately the post office realized that there were significant advantages, such as the chance of generating more revenue through passengers and large parcels.

With the advent of the locomotive and rail transit, the mail coach was quickly phased out. Carrying mail by train had obvious advantages which made post coaches obsolete. However, several examples of mail coaches have been preserved in museums, for people who are interested in seeing what a mail coach looked like, and it is also possible to ride in a replica mail coach, for those who want a personal experience.