Macha, daughter of Ernmas, of the Tuatha Dé Danann, appears in many early sources. She is often mentioned together with her sisters, the Morrígan (Anann) and the Badb, and the three are often considered a triple goddess associated with war. O'Mulconry's Glossary, a thirteenth century compilation of glosses from medieval manuscripts preserved in the Yellow Book of Lecan, describes Macha as "one of the three morrígna" (the plural of Morrígan), and says the term Mesrad Machae, "the mast [acorn crop] of Macha", refers to "the heads of men that have been slaughtered." A version of the same gloss in MS H.3.18 identifies Macha with the Badb, calls the trio "raven women" who instigate battle. Keating explicitly calls them "goddesses", but medieval Irish tradition was keen to remove all trace of pre-Christian religion, so Macha is said to have been killed by Balor in the Second Battle of Mag Tuired.

A number of figures called Macha appear in Irish mythology, legend and historical tradition, all believed to derive from the same deity.