Emona or Aemona, short for Colonia Iulia (A)emona, is a Roman castrum founded in 14/15 CE, possibly by the XV Legio Apollinaris (theory proposed by the noted historian and epigraphy expert Balduin Saria), on a territory already populated by ancient settlers of uncertain origin.

Situated on the Ljubljanica River near its junction with the Sava, its location overlaps with the southwestern part of the old nucleus of the modern city of Ljubljana, capital of Slovenia, where numerous remains of Emona can still be seen today (substantial parts of the ancient city walls, several mosaics, parts of the paleochristian baptistry, residential houses, statues, tombstones etc.).

(A)emona is, along with Nauportus, Celeia and Poetovio, one of the main cities on the eastern coast of the Adriatic.

Formerly, it was assumed to have been a part of the Roman province of Pannonia.

However, recent research seems to indicate that Aemona was actually the easternmost city of the Roman empire proper.