The term "Eventer" or "Event Horse" describes horses specifically bred, selected, and trained for eventing competition rather than designating a distinct breed. Eventing, also called "horse trials" or historically "three-day eventing," represents the equestrian triathlon combining dressage (testing obedience, suppleness, and harmony), cross-country (testing courage, stamina, and jumping ability over solid obstacles on varied terrain), and show jumping (testing carefulness, precision, and remaining energy after cross-country). This demanding sport requires horses possessing exceptional versatility, as they must excel at three very different disciplines requiring distinct physical and mental attributes rarely combined in single individuals.
Most competitive event horses come from Thoroughbred or Thoroughbred-cross backgrounds, particularly crosses with European warmbloods creating horses combining Thoroughbred courage, speed, and stamina with warmblood power, trainability, and jumping technique. Pure Thoroughbreds compete successfully particularly at lower levels and in certain regions, while warmblood crosses dominate upper levels where additional power and scope prove advantageous. Other breeds competing in eventing include Irish Sport Horses (Thoroughbred-Irish Draught crosses), Anglo-Arabs, various European warmbloods, and occasionally Quarter Horses, Morgans, or other versatile breeds, though Thoroughbred influence remains dominant across competitive levels.
No single registry governs event horses, as multiple breed organizations and sport horse studbooks maintain records for their respective breeds while eventing itself is governed internationally by the Fédération Équestre Internationale (FEI). National organizations including United States Eventing Association (USEA), British Eventing, Eventing Australia, and similar bodies in other countries organize competitions from introductory levels through advanced, promote the sport, and provide educational resources. Competition levels range from Beginner Novice through Advanced/CCI5* (five-star international competition), with each level increasing demands on horse and rider combinations requiring years of systematic development progressing through levels appropriately.
Understanding that event horses represent functional types selected for specific athletic abilities rather than breed alone helps clarify that success depends on individual horses' qualities across multiple disciplines, training, and partnership with skilled riders. Certain breeding programs have proven particularly successful producing event horses including Irish Sport Horse breeding, specific Thoroughbred bloodlines, and European warmblood-Thoroughbred crosses, though ultimately individual horses' courage, athleticism, trainability, and soundness determine competitive potential regardless of pedigree alone.

