The gens Marcia, occasionally written Martia, was one of the oldest and noblest houses at ancient Rome. They claimed descent from the second and fourth Roman Kings, and the first of the Marcii appearing in the history of the Republic would seem to have been patrician; but all of the families of the Marcii known in the later Republic were plebeian. The first to obtain the consulship was Gaius Marcius Rutilus in 357 BC, only a few years after the passage of the lex Licinia Sextia opened this office to the plebeians.
The Marcii are supposed to have been Sabines, descended from a certain Marcus Marcius of Cures, a kinsman of Numa Pompilius, and his son, Numa Marcius, a childhood friend of Pompilius, who accompanied him to Rome and served as his chief advisor. His son, the younger Numa Marcius, was urban prefect under Tullus Hostilius, and his grandson was Ancus Marcius, the fourth King of Rome.
Although the Roman monarchy was not strictly hereditary, tradition holds that the sons of Ancus Marcius hoped to succeed their father, but were prevented from doing so when his chief advisor, the Etruscan Lucius Tarquinius, took advantage of their absence at the time of the king's death to solicit support for his own claim, and was elected king.
After biding their time for many years, the sons of Marcius gained their revenge by engineering the assassination of Tarquin, but they were again prevented from claiming the throne by a ruse of Tanaquil, the Roman queen, who installed her stepson, Servius Tullius, as regent, until he had sufficient support to rule on his own. The later Marcii claimed descent from Ancus Marcius, but nothing further is recorded of his sons or the generations between them and the Marcii of the early Republic.