A kouros (Ancient Greek: κοῦρος, plural kouroi) is the modern term given to free-standing ancient Greek sculptures which first appear in the Archaic period in Greece and represent nude male youths. In Ancient Greek kouros means "youth, boy, especially of noble rank". The term kouros was first proposed for what were previously thought to be depictions of Apollo by V. I. Leonardos in 1895 in relation to the youth from Keratea, and adopted by Henri Lechat as a generic term for the standing male figure in 1904. Such statues are found across the Greek-speaking world; the preponderance of these were found in sanctuaries of Apollo with more than one hundred from the sanctuary of Apollo Ptoios, Boeotia, alone. These free-standing sculptures were typically marble, but the form is also rendered in limestone, wood, bronze, ivory and terracotta. They are typically life-sized, though early colossal examples are up to 3 meters tall.
The female sculptural counterpart of the kouros is the kore.
In Ancient Greek kouros means "youth, boy, especially of noble rank." When a pubescent was received into the body of grown men, as a grown Kouros, he could enter the initiation fest of the brotherhood (φρατρία). Apellaios was the month of these rites, and Apollo (Apellon) was the "megistos kouros" (the great Kouros).
The kouros type appears to have served several functions. It was previously thought that it was used only to represent the god Apollo, as attested by its depiction on a vase painting in the presence of supplicants. This association with Apollo was supported by the description of the statue of the Pythian Apollo at Samos by Diodoros as "Egyptian in style, with his arms hanging by his sides and his legs parted". However, not all kouroi are images of a deity; many have been discovered in cemeteries where they most likely served as commemorative tombstones of the deceased, also the type was used as a memorial for victors in the games (like trophies), kouroi were used as offerings to the gods, (Pausanias describes the statue of Arrhichion, an Olympic pankratiast, as in the kouros scheme), and some kouroi have been found in sanctuaries other than that of Apollo. Indeed, some kouroi placed in sanctuaries were not inscribed with the name of the god but with a mortal, for example the 'Delphi Twins' Kleobis and Biton were honoured for their piety with matching kouroi.