A stele ( STEE-lee), or occasionally stela (plural stelas or stelæ), when derived from Latin, is a stone or wooden slab, generally taller than it is wide, erected in the ancient world as a monument. The surface of the stele often has text, ornamentation, or both. These may be inscribed, carved in relief, or painted.

Stelae were created for many reasons. Grave stelae were used for funerary or commemorative purposes. Stelae as slabs of stone would also be used as ancient Greek and Roman government notices or as boundary markers to mark borders or property lines. Stelae were occasionally erected as memorials to battles. For example, along with other memorials, there are more than half-a-dozen steles erected on the battlefield of Waterloo at the locations of notable actions by participants in battle.

A traditional Western gravestone (headstone, tombstone, gravestone, or marker) may technically be considered the modern equivalent of ancient stelae, though the term is very rarely applied in this way. Equally, stele-like forms in non-Western cultures may be called by other terms, and the words "stele" and "stelae" are most consistently applied in archaeological contexts to objects from Europe, the ancient Near East and Egypt, China, and sometimes Pre-Columbian America.