Before the Roman conquest, the ancient Abellinum was a centre of the Samnite Hirpini.
The town was Christianized around 500 AD, becoming an episcopal seat. There followed the invasions of the Goths and Vandals. Subsequently Avellino became a Lombard centre, with a castle on the Terra hill. In the early Middle Ages it was part of the Duchy (later Principality) of Benevento and, after the latter’s fall, of the Principality of Salerno.
In 1100, during the Norman rule of southern Italy, it was acquired by Riccardo dell’Aquila. Later King Charles I of Anjou assigned it to the Montfort family, who were succeeded by the Del Balzo and the Filangierian of the House of Candia.
The feudal rights to Avellino were purchased in 1581 by Don Marino I Caracciolo, duke of Atripalda, of a patrician family of Naples, who was made Prince of Avellino in 1589. Avellino became the main seat of the Caracciolo. Don Marino’s son and grandson were consecutively Grand Chancellor of the Kingdom of Naples and chevaliers of the Order of the Golden Fleece. The grandson, Don Marino II (1587–1630), was the patron of Giambattista Basile, author of the Pentamerone.
In 1820 Avellino was seat of revolutionary riots. However, the Unification of Italy some fifty years later did not bring any benefit to the city, being cut off from the main railway line Naples-Benevento-Foggia, and far from the sea as well.
In 1943 the city was bombed by Allied planes in an attempt to cut off the retreat of German panzer units over the important Bridge of Ferriera.
Avellino has suffered from seismic activity throughout its history and was struck hard by the earthquakes of 23 November 1980 and 14 February 1981. Avellino has also received ashfall from numerous eruptions of Vesuvius which lies almost due west; the city is the type locality of pumice deposited from a Plinian eruption of Vesuvius about 3800 years ago