The domestication of horses and adoption of horse riding were critical processes that culminated in the emergence of mounted warriors and nomadic empires that shaped world history. The constraints of horse biology and riding equipment meant that equine veterinary care, particularly of teeth, was a core component of the success of the human–horse relationship. We report the earliest evidence of equine dentistry, from the Mongolian Steppe, at 1150 BCE. Key shifts in equine dentistry practice through time can be linked first to the emergence of horseback riding and later to the use of metal bits that enabled better control of horses. The maintenance of horse health through dentistry underwrote the key role of horses in cultures and economies around the world.