Hyracotherium is the extinct ancestor of modern horses. It is also known as the dawn horse. Hyracotherium lived about 50 million years ago, during the Paleogene Period. These animals were once present in what are now Europe and North America.

The main stream of horse evolution occurred on the North American continent. Compared to living horses, Hyracotherium was a lot smaller: it usually measured half a metre or less (1.5 ft.) in length—about the size of a fox terrier.

Also, it had a more-complete series of teeth than modern horses, which were used for feeding on soft, leafy vegetation. Its legs ended with three toes on the hind feet and with four toes on the forefeet. Each toe had a pad on its underside, like dogs. The long legs of modern horses end in a single, powerful toe with a hoof (not a pad).