The Antoninianus was the Roman silver coin that replaced the denarius as the main imperial silver denomination.
The coin was introduced during the reign of Caracalla, probably in 215 CE. Its modern name comes from Caracalla’s official name, Antoninus. Although it was intended to represent two denarii, its actual silver content was less than twice that of a denarius, making it an early sign of monetary debasement.
The antoninianus became especially common during the third-century crisis, when emperors needed money for armies and administration. Over time, the silver content declined sharply, and many later examples were mainly bronze with a thin silver coating created by surface enrichment.
The coin is recognizable in many issues because the emperor’s portrait usually wears a radiate crown. Empresses often appear seated on a crescent moon. The denomination eventually gave way to later reforms, especially Diocletian’s monetary restructuring.