Linear A is a writing system that was used by the Minoans of Crete from 1800 BC to 1450 BC. Linear A was the primary script used in palace and religious writings of the Minoan civilization. It was succeeded by Linear B, which was used by the Mycenaeans to write an early form of Greek. It was discovered by the archaeologist Sir Arthur Evans in 1900. No texts in Linear A have yet been deciphered. Evans named the script "Linear" because its characters consisted simply of lines inscribed in clay, in contrast to the more pictographic characters in Cretan hieroglyphs that were used during the same period.

Many undeciphered writing systems exist today; most date back several thousand years, although some more modern examples do exist. The term "writing systems" is used here loosely to refer to groups of glyphs which appear to have representational symbolic meaning, but which may include "systems" that are largely artistic in nature and are thus not examples of actual writing.