A star war was a decisive conflict between rival polities of the Maya civilization during the first millennium AD. The term comes from a specific type of glyph used in the Maya script, which depicts a star showering the earth with liquid droplets, or a star over a shell. It represents a verb but its phonemic value and specific meaning have not yet been deciphered. The name "star war" was coined by the epigrapher Linda Schele to refer to the glyph, and by extension to the type of conflict that it indicates.
Maya inscriptions assign episodes of Maya warfare to four distinct categories, each represented by its own glyph. Those accorded the greatest significance by the Maya were described with the "star war" glyph, representing a major war resulting in the defeat of one polity by another. This represents the installation of a new dynastic line of rulers, complete dominion of one polity over another, or a successful war of independence by a formerly dominated polity.
Losing a star war could be disastrous for the defeated party. The first recorded star war in 562, between Caracol and Tikal, resulted in a 120-year hiatus for the latter city. It saw a decline in Tikal's population, a cessation of monument erection, and the destruction of certain monuments in the Great Plaza. When Calakmul defeated Naranjo in a star war on December 24, 631, it resulted in Naranjo's ruler being tortured to death and possibly eaten. Another star war in February 744 resulted in Tikal sacking Caracol and capturing a personal god effigy of its ruler. An inscription from a monument found at Tortuguero (dating from 669) describes the aftermath of a star war: "the blood was pooled, the skulls were piled".
Mayanists have noted that the dates of recorded star wars often coincide with astronomical events involving the planet Venus, either when it was first visible in the morning or night sky or during its absence at inferior conjunction. Venus was known to Mesoamerican civilizations as the bringer of war (in contrast to the equivalent European belief assigning that characteristic to Mars). The Maya called it Chak Ek' or "Great Star" and made it the focus of detailed astronomical observation and calculation. The Dresden Codex, one of only four surviving Maya books, includes astronomical tables for calculating the position of Venus, which the codex depicts as spearing people as it passes overhead.