A horse trailer or horse van (also called a horse float in Australia and New Zealand or horsebox in the British Isles) is used to transport horses. There are many different designs, ranging in size from small units capable of holding two or three horses, able to be pulled by a pickup truck or SUV; to gooseneck designs that carry six to eight horses, usually pulled by 1-ton dually-style pickups. There are also large semi-trailers that can haul a significant number of animals. In the UK, a horsebox may also refer to a motorised vehicle adapted to carry horses (generally known as a horse van in North America or Australasia), or a railway vehicle specifically designed to carry horses.

The least expensive type of trailer is the stock trailer, a trailer designed for cattle that is enclosed on the bottom, but has slits at roughly the eye level of the animals to allow ventilation. Trailers designed specifically for horses are more elaborate. Because horses are usually hauled for the purpose of competition or work, where they must arrive in peak physical condition, horse trailers are designed for the comfort and safety of the animals. They usually have adjustable vents and windows as well as suspension designed to provide a smooth ride and less stress on the animals.