Ancient Sutrium occupied an important position, commanding as it did the road into Etruria, the later Via Cassia: Livy describes it as one of the keys of Etruria, nearby Nepi being the other. It came into the hands of Rome after the fall of Veii, and a Latin colony was founded there; it was lost again in 386 BC, but was recovered and recolonized around 383 BC. It was besieged by the Etruscans in 311–310 BC, but not taken. With Nepi and ten other Latin colonies it refused further help in the Second Punic War in 209 BC. Its importance as a fortress explains, according to Festus, the proverb Sutrium ire, of one who goes on important business, as it occurs in Plautus. It is mentioned in. the war of 41 BC, and received a colony of veterans under the triumviri (Colonia coniuncta lulia Sutrina). Inscriptions show that it was a place of some importance under the empire, and it is mentioned as occupied by the Lombards.

Sutri retained its strategic importance as a fortified place near the borders of the Duchy of Rome. The Donation of Sutri was an agreement reached at Sutri between the Lombard king Liutprand the Lombard and Pope Gregory II in 728. At Sutri the two reached an agreement, by which Sutri and some hill towns in Latium (see Vetralla) were given to the Papacy, "as a gift to the blessed Apostles Peter and Paul" according to the Liber Pontificalis. The pact formed the first extension of Papal territory beyond the confines of the Duchy of Rome. An important hoard of jewellery dating from this time, known as the Sutri Treasure, was found near the town in the 19th century. It is now in the British Museum.[1]

Sutri, the seat of a bishopric (see below), was retrieved for the Papacy after the defeat of the Lombards.

Pope Gregory VI abdicated at Sutri on December 20, 1046, following the Synod of Sutri convened at the request of Emperor Henry III. In 1111 it was the seat of the treaty between Paschal II and Emperor Henry V; in 1146 and 1244 Eugene III and Innocent IV took refuge here, respectively. In 1244 it was conquered by Pietro di Vico, but was later taken by Pandolfo, count of Anguillara, who gave it back to the Papal States.

The city witnessed the struggles between Guelphs and Ghibellines. In 1433 the condottiero Niccolò Fortebraccio set fire to Sutri, and from that point onward the city declined in favour of Ronciglione.