Mars was the great Roman god of war, the father of Romulus. The well-known name, like a number of other well-known names, is still of uncertain meaning, although it is known that an earlier form of it had been Mavors, and in some dialects Mamers.

Among attempts to interpret the name have been the following: from Greek marnamai, 'to fight', 'do battle', a suitably belligerent name; from Latin mas, 'virility', a literally masculine or male name; from an old Latin root mar-, 'to shine', appropriate for a sun god. Perhaps the name may ultimately link up with a Sanskrit word mrnati meaning 'striker', 'crusher'.

We can be certain, at least, that he gave his name to the month of March (Latin Martius mensis). The earlier Greek name of Mars the planet was Pyroeis, 'fiery' (compare Pyrrha and Pyrrhus), doubtless for its blood-red colour. This later became Ares, the name of his Greek counterpart, and finally Mars.