Centaur

A Centaur (Κένταυρος in Ancient Greek) is a half horse, half human. They are known to be great partiers (aside from Chiron.). They can be any color.

History
The Centaurs are best known for their fight with the lapithae, caused by their attempt to carry off Hippodamia and the rest of the Lapith women, on the day of her marriage to Pirithous, king of the Lapithae, himself the son of Ixion.

Centaurs were notorious for being overly indulgent drinkers and carousers, given to violence when intoxicated, and generally uncultured delinquents. Each Centaur was also wild and lusty, except for the most well-known centaur, Chiron. True centaurs were born of sun and raincloud, until the female centaurs (called Centauresses) came from some normal horses, and centaurs started out like normal creatures, from conceived from baby to adult.

The Lightning Thief
One known serious centaur is Chiron, the activities director at Camp Half-Blood, and appears throughout the rest of the series.

The Sea of Monsters
When Percy Jackson was fighting with Luke Castellan The centaur organization, the Party Ponies, make an appearance.

The Battle of the Labyrinth
At least one centaur is known to have been defeated by a Giant under orders from Antaeus in The Battle of the Labyrinth.

The Last Olympian
The Party ponies, commanded by Chiron, assist the demigods in The Battle of Manhattan, though Percy sees none other than Chiron at the end of the battle. He deduces that they were either killed or ran away.

Female Centaurs
It is unknown if there are female centaurs, but they are not mentioned in the series.