The Isthmian script is an early set of symbols found in inscriptions around the Isthmus of Tehuantepec, dating to c. 500 BCE – 500 CE, though with dates subject to disagreement. It is also called the La Mojarra script and the Epi-Olmec script ('post-Olmec script').
It has not been conclusively determined whether Isthmian script is a true writing system that represents a spoken language, or is a system of proto-writing. According to a disputed partial decipherment, it is structurally similar to the Maya script, and like Maya uses one set of characters to represent morphemes, and a second set to represent syllables.