In ancient Roman religion and myth, Mars (Latin: Mārs, pronounced [maːrs]) was the god of war and also an agricultural guardian, a combination characteristic of early Rome. He was the son of Jupiter and Juno, and he was the most prominent of the military gods in the religion of the Roman army. Most of his festivals were held in March, the month named for him (Latin Martius), and in October, which began the season for military campaigning and ended the season for farming.

Under the influence of Greek culture, Mars was identified with the Greek god Ares,[4] whose myths were reinterpreted in Roman literature and art under the name of Mars. But the character and dignity of Mars differed in fundamental ways from that of his Greek counterpart, who is often treated with contempt and revulsion in Greek literature. Mars's altar in the Campus Martius, the area of Rome that took its name from him, was supposed to have been dedicated by Numa, the peace-loving semi-legendary second king of Rome. Although the center of Mars's worship was originally located outside the sacred boundary of Rome (pomerium), Augustus made the god a renewed focus of Roman religion by establishing the Temple of Mars Ultor in his new forum.

Although Ares was viewed primarily as a destructive and destabilizing force, Mars represented military power as a way to secure peace, and was a father (pater) of the Roman people. In the mythic genealogy and founding myths of Rome, Mars was the father of Romulus and Remus by his rape of Rhea Silvia. His love affair with Venus symbolically reconciled the two different traditions of Rome's founding; Venus was the divine mother of the hero Aeneas, celebrated as the Trojan refugee who "founded" Rome several generations before Romulus laid out the city walls.

Ares (/ˈɛəriːz/; Ancient Greek: Ἄρης, Árēs [árɛːs]) is the Greek god of courage and war. He is one of the Twelve Olympians, and the son of Zeus and Hera. In Greek literature, he often represents the physical or violent and untamed aspect of war and is the personification of sheer brutality and bloodlust, in contrast to his sister, the armored Athena, whose functions as a goddess of intelligence include military strategy and generalship.

The Greeks were ambivalent toward Ares: although he embodied the physical valor necessary for success in war, he was a dangerous force, "overwhelming, insatiable in battle, destructive, and man-slaughtering. His sons Phobos (Fear) and Deimos (Terror) and his lover, or sister, Eris (Discord) accompanied him on his war chariot. In the Iliad, his father Zeus tells him that he is the god most hateful to him. An association with Ares endows places and objects with a savage, dangerous, or militarized quality.[6] His value as a war god is placed in doubt: during the Trojan War, Ares was on the losing side, while Athena, often depicted in Greek art as holding Nike (Victory) in her hand, favoured the triumphant Greeks.

Ares plays a relatively limited role in Greek mythology as represented in literary narratives, though his numerous love affairs and abundant offspring are often alluded to. When Ares does appear in myths, he typically faces humiliation. He is well known as the lover of Aphrodite, the goddess of love, who was married to Hephaestus, god of craftsmanship. The most famous story related to Ares and Aphrodite shows them exposed to ridicule through the wronged husband's device.

The counterpart of Ares among the Roman gods is Mars, who as a father of the Roman people was given a more important and dignified place in ancient Roman religion as a guardian deity. During the Hellenization of Latin literature, the myths of Ares were reinterpreted by Roman writers under the name of Mars. Greek writers under Roman rule also recorded cult practices and beliefs pertaining to Mars under the name of Ares. Thus in the classical tradition of later Western art and literature, the mythology of the two figures later became virtually indistinguishable.