This is the name given to a variety of sports using horses, other than traditional horse-racing.
The three most well known disciplines are show-jumping, dressage and cross-country. They are sometimes combined to make a horsey triathlon called 3-Day Eventing.
Show-jumping sees horse and rider try to jump over between 12 and 15 fences in a sand or grass area against the clock. If they knock a fence down they are docked penalty points or time penalties.
Cross-country is similar but instead of an enclosed arena the fences are spread around a course that goes through the countryside. They have to get over 45 fences spread over almost 6,000m.
Dressage tests the rider and horse's ability to complete a series of moves and walks. They are marked by a set of judges.
It's supposed to look like the horse is doing all the work on their own, without the rider telling them what to do.
There are a number of other equestrian sports too though, like polo, paradressage and vaulting (which is gymnastics on horseback!).
If you want to try equestrian sport, then click on the link to the British Equestrian Federation on the right hand side of this page.