In the prehistoric era, Friuli was home to the Castellieri culture.
These peoples most likely arrived from the sea and were the dominant culture in the area from about the 15th century BC until the early historical period.
During the course of the 4th century BC the Carni (in ancient Greek Καρνίοι), a tribe of unknown ethnicity which may have spoken a Celtic, a Venetic or a Rhaetic language, and who introduced advanced techniques of working iron and silver settled Friuli.
According to Strabo [4.6] the Carni inhabited "the country about the Adriatic Gulf and Aquileia" and both Pliny [3.22(18)] and Ptolemy [3.1] ascribe Aquileia, Concordia and Forum Julii to belong to the "towns of the Carni" in the "country of the Carni".
The Carni worshiped the deity Belenus which is attested by the most numerous votive inscriptions found in and around Aquileia.
A northern mountainous area of Friuli still retains the ancient name Carnia.

Beginning from the 2nd century BC, Friuli was colonized by the Romans: Aquileia was the fourth largest city of Italy during Roman imperial times, capital of Regio X of the Italia province (the Augustan region Venetia et Histria).
The city was the most important river port on the Natissa river, dominating trade between the Adriatic Sea and northern Europe (carried over the Via Iulia Augusta road).
Aquileia owed its importance to the strategic position it has on the Adriatic sea and its proximity to the Alps.
This location allowing Rome to intercept barbarian invasions from the East.
Julius Caesar quartered his legions in Aquileia during winter.
The development of other centers, such as Forum Iulii (Cividale del Friuli) and Iulium Carnicum (Zuglio), contributed to the increase in economic and cultural wealth of Friuli until the first barbarian incursions, at the beginning of the 5th century.
In the final decades of the 3rd century, Aquileia became the center of one of the most prestigious bishoprics of the empire, competing in Italy with Milan and, subsequently, Ravenna, for second place to Rome.
A Hun invasion marked the start of Friuli's decline: Aquileia, protected by meager forces, was forced to surrender and was razed to the ground by Attila in 452.
After the retreat of the Huns, the survivors, who had found shelter in the lagoon of Grado, returned to the city, but found it completely destroyed.
The reconstruction of Aquileia was never completed and it never regained the old splendour of the capital of X Regio.
The city remained important even after the fall of the Western Roman Empire, due to the creation of the Patriarchate of Aquileia.
It ranked among the highest ecclesiastic authorities in Italy from the mid-6th century onward.
The lack of security in the Friulian plain, crossroads of all the great barbarian invasions, drove many people to seek shelter on the islands of the lagoons or in fortified hill-villages, causing a generalized depopulation of the more fertile part of the region and its consequent colonization by barbarian gentes.
In the prehistoric era, Friuli was home to the Castellieri culture. These peoples most likely arrived from the sea and were the dominant culture in the area from about the 15th century BC until the early historical period. During the course of the 4th century BC the Carni (in ancient Greek Καρνίοι), a tribe of unknown ethnicity which may have spoken a Celtic, a Venetic or a Rhaetic language, and who introduced advanced techniques of working iron and silver settled Friuli. According to Strabo [4.6] the Carni inhabited "the country about the Adriatic Gulf and Aquileia" and both Pliny [3.22(18)] and Ptolemy [3.1] ascribe Aquileia, Concordia and Forum Julii to belong to the "towns of the Carni" in the "country of the Carni". The Carni worshiped the deity Belenus which is attested by the most numerous votive inscriptions found in and around Aquileia. A northern mountainous area of Friuli still retains the ancient name Carnia.
Beginning from the 2nd century BC, Friuli was colonized by the Romans: Aquileia was the fourth largest city of Italy during Roman imperial times, capital of Regio X of the Italia province (the Augustan region Venetia et Histria). The city was the most important river port on the Natissa river, dominating trade between the Adriatic Sea and northern Europe (carried over the Via Iulia Augusta road). Aquileia owed its importance to the strategic position it has on the Adriatic sea and its proximity to the Alps. This location allowing Rome to intercept barbarian invasions from the East. Julius Caesar quartered his legions in Aquileia during winter. The development of other centers, such as Forum Iulii (Cividale del Friuli) and Iulium Carnicum (Zuglio), contributed to the increase in economic and cultural wealth of Friuli until the first barbarian incursions, at the beginning of the 5th century. In the final decades of the 3rd century, Aquileia became the center of one of the most prestigious bishoprics of the empire, competing in Italy with Milan and, subsequently, Ravenna, for second place to Rome. A Hun invasion marked the start of Friuli's decline: Aquileia, protected by meager forces, was forced to surrender and was razed to the ground by Attila in 452. After the retreat of the Huns, the survivors, who had found shelter in the lagoon of Grado, returned to the city, but found it completely destroyed. The reconstruction of Aquileia was never completed and it never regained the old splendour of the capital of X Regio. The city remained important even after the fall of the Western Roman Empire, due to the creation of the Patriarchate of Aquileia. It ranked among the highest ecclesiastic authorities in Italy from the mid-6th century onward. The lack of security in the Friulian plain, crossroads of all the great barbarian invasions, drove many people to seek shelter on the islands of the lagoons or in fortified hill-villages, causing a generalized depopulation of the more fertile part of the region and its consequent colonization by barbarian gentes.
Friuli