Samnium (Italian: Sannio) is a Latin exonym for a region of south or south and central Italy in Roman times.

The name survives in Italian today, but today's territory comprising it is only a small portion of what it once was.

The populations of Samnium are called Samnites by the Romans.

Their own endonyms are Safinim for the country (attested in one inscription and one coin legend) and Safineis for the people.The language of these endonyms and of the population is the Oscan language.

However, not all the Samnites speak Oscan, and not all the Oscan speakers live in Samnium.The ancient authors are unable to relay a precise definition of Samnium's borders.

Moreover, the regions included vary depending on the time period considered.

The main configurations are the borders that it has during the floruit of the Oscan speakers, from about 600 BCE to about 290 BCE, known historically in the Roman Republic, and the borders as they are defined to be by the emperor Augustus, published in his official manifesto, Discriptio Italiae, lost to moderns, but serving as the basis of Pliny the Elder's description of Italy.

By this time Oscan is not spoken.

Samnium had ceased to be a sovereign state since about 290 BCE.

Augustus divides Italy into 11 regions.

Samnium Is Region IV.

It includes areas that had never been in the republican Samnium and also omits much of it.

Ancient Samnium Is included in three of Augustus' regions.