In ancient Roman religion, the Flamen Martialis was the high priest of the official state cult of Mars, the god of war.
Among his duties was the ritual brandishing of the sacred spears of Mars when the Roman army was preparing for war.
Like other flamines maiores, the high priest of Mars was a patrician and required to marry through the ceremony of confarreatio.
At the Larentalia in April, the Flamen Martialis poured libations in honour of Acca Laurentia, wife of Faustulus, the foster-father of the Rome's twin founders, Romulus and Remus.
In the 240s BC, for instance, the consul Aulus Postumius Albinus could not assume his military command, because the pontifex maximus Lucius Caecilius Metellus invoked the prohibition against a Flamen Martialis leaving the city.