In ancient Greek religion and mythology, Helios is the god who personifies the Sun. His name is also Latinized as Helius, and he is often given the epithets Hyperion and Phaethon. Helios is often depicted in art with a radiant crown and driving a horse-drawn chariot through the sky. He was a guardian of oaths and also the god of sight. Though Helios was a relatively minor deity in Classical Greece, his worship grew more prominent in late antiquity thanks to his identification with several major solar divinities of the Roman period, particularly Apollo and Sol. The Roman Emperor Julian made Helios the central divinity of his short-lived revival of traditional Roman religious practices in the 4th century AD.

Religious practices in ancient Greece encompassed a collection of beliefs, rituals, and mythology, in the form of both popular public religion and cult practices. The application of the modern concept of "religion" to ancient cultures has been questioned as anachronistic. The ancient Greeks did not have a word for 'religion' in the modern sense. Likewise, no Greek writer known to us classifies either the gods or the cult practices into separate 'religions'. Instead, for example, Herodotus speaks of the Hellenes as having "common shrines of the gods and sacrifices, and the same kinds of customs."