Hippeis is a Greek term for cavalry. In ancient Athenian society, after the political reforms of Solon, the hippeus was the second highest of the four social classes. It was composed of men who had at least 300 medimnoi or their equivalent as yearly income. According to the Timocratic Constitution the average citizen had a yearly income of less than 200 medimnoi. This gave the men who made 300 medimnoi the ability to purchase and maintain a war horse during their service to the state.

The Solonian constitution was created by Solon in the early 6th century BC. At the time of Solon, the Athenian State was almost falling to pieces in consequence of dissensions between the parties into which the population was divided. Solon wanted to revise or abolish the older laws of Draco. He promulgated a code of laws embracing the whole of public and private life, the salutary effects of which lasted long after the end of his constitution.