In ancient Roman religion and myth, Jupiter (Latin: Iuppiter) or Jove is the king of the gods and the god of sky and thunder. Jupiter was the chief deity of Roman state religion throughout the Republican and Imperial eras, until the Empire came under Christian rule. In Roman mythology, he negotiates with Numa Pompilius, the second king of Rome, to establish principles of Roman religion such as sacrifice.

Jupiter is usually thought to have originated as a sky god. His identifying implement is the thunderbolt, and his primary sacred animal is the eagle, which held precedence over other birds in the taking of auspices and became one of the most common symbols of the Roman army (see Aquila). The two emblems were often combined to represent the god in the form of an eagle holding in its claws a thunderbolt, frequently seen on Greek and Roman coins. As the sky-god, he was a divine witness to oaths, the sacred trust on which justice and good government depend. Many of his functions were focused on the Capitoline ("Capitol Hill"), where the citadel was located. He was the chief deity of the early Capitoline Triad with Mars and Quirinus. In the later Capitoline Triad, he was the central guardian of the state with Juno and Minerva. His sacred tree was the oak.