(French courier, to run), a messenger sent post or express with despatches.

The couriers employed by the ancients were of two kinds; first, those who ran on foot, called by the Greeks hemerodromi, or day-runners, regarding whom Pliny, Cornelius Nepos, and Caesar mention that some of them would run twenty, thirty, thirty-six, and in the circus even forty leagues a-day; second, riding couriers (cursores equitantes), who changed horses as modern couriers do.

Xenophon attributes the first couriers to Cyrus. Herodotus says they were very common among the Persians, and that there was nothing in the world more swift than such messengers. That prince, says Xenophon, proved how far a horse could run in a day, and built stables at corresponding distances; and at each station a courier was always ready with a fresh horse to forward the packet to the next stage, and so on throughout the empire.

But it does not appear that either the Greeks or Romans had any regular system of couriers till the time of Augustus. Under that prince they travelled in cars, though it would appear that they afterwards went on horseback. Under the Western Empire they were called viatores; and under that of Constantinople cursores.