After the collapse of the Western Roman Empire, Friuli belonged to the kingdom of Odoacer and subsequently to that of Theodoric the Great.
The Byzantine reconquest under Justinian I was brief in the region, in 568 it was one of the first provinces conquered by the Lombards, who invaded from Pannonia, and with that, ended the Greek-Byzantine era of the region.
The Lombard king Alboin established the Duchy of Friuli, the first Lombard duchy, and granted it to his relative Gisulf I. The capital of the duchy was established at Forum Iulii (Cividale del Friuli), which became the most important city of the area and for where it derived its name.

The duchy of Friuli was from the start one of the most important Lombard duchies.
It served as a barrier against the threat of invasion by the Avars and Slavs from Pannonia.
Among the duchies of the North, which were closely aligned with the crown (unlike Spoleto and Benevento to the South), it was the most powerful, probably due to its marcher status.
Among later dukes, Ratchis became king in 744 and his ducal successor, Aistulf, succeeded him as king in 749.
The historian Paul the Deacon was born in Friuli (730/5), he went on to write the Historia Langobardorum and taught Latin grammar at Charlemagne's court.
 Another teacher and a trusted advisor Charlemagne's court, Paulinus, was born at Cividale and eventually became patriarch of Aquileia.

After the Kingdom of Italy fell to the Franks, the duchy of Friuli was reorganized into counties according to the Frankish model.
The region was again reorganized into the March of Friuli in 846.
The march was granted to the Unruoching dynasty.
Friuli became the base of power of Berengar I during his struggles for the throne of Italy between 888 and 924.

The march was transformed under his rule, its territory extended to Lake Garda, the capital moved to Verona, and a new March of Verona and Aquileia established in its place.
The territory was now subjected to the Duchy of Bavaria, then to the Duchy of Carinthia, for more than a century.

On 3 April 1077, the Emperor Henry IV granted the county of Friuli, with ducal status, to Sigaerd, Patriarch of Aquileia.
In the succeeding centuries, the patriarchate expanded its control over neighboring Trieste, Istria, Carinthia, Styria, and Cadore.
The patriarchal state of Friuli was one of the best organized polities of the Italian Middle Ages.
From the 12th century it possessed a parliament representing the communes as well as the nobility and the clergy.
This institution only survived six centuries, remaining alive yet weak even during Venetian domination.
It convened for the last time in 1805, when it was abolished by Napoleon Bonaparte.
The Patriarch Marquard of Randeck (1365–1381) had gathered together and codified all the laws of Friuli and promulgated them as the Constitutiones Patriae Foriiulii ("Constitutions of the Country of Friuli").
Cividale del Friuli was seat of the Patriarchate until 1238, when the patriarch moved his seat to Udine, where he had a magnificent episcopal edifice constructed.
Udine was so important that it in time became the institutional capital of Friuli.
After the collapse of the Western Roman Empire, Friuli belonged to the kingdom of Odoacer and subsequently to that of Theodoric the Great. The Byzantine reconquest under Justinian I was brief in the region, in 568 it was one of the first provinces conquered by the Lombards, who invaded from Pannonia, and with that, ended the Greek-Byzantine era of the region. The Lombard king Alboin established the Duchy of Friuli, the first Lombard duchy, and granted it to his relative Gisulf I. The capital of the duchy was established at Forum Iulii (Cividale del Friuli), which became the most important city of the area and for where it derived its name.
The duchy of Friuli was from the start one of the most important Lombard duchies. It served as a barrier against the threat of invasion by the Avars and Slavs from Pannonia. Among the duchies of the North, which were closely aligned with the crown (unlike Spoleto and Benevento to the South), it was the most powerful, probably due to its marcher status. Among later dukes, Ratchis became king in 744 and his ducal successor, Aistulf, succeeded him as king in 749. The historian Paul the Deacon was born in Friuli (730/5), he went on to write the Historia Langobardorum and taught Latin grammar at Charlemagne's court.  Another teacher and a trusted advisor Charlemagne's court, Paulinus, was born at Cividale and eventually became patriarch of Aquileia.
After the Kingdom of Italy fell to the Franks, the duchy of Friuli was reorganized into counties according to the Frankish model. The region was again reorganized into the March of Friuli in 846. The march was granted to the Unruoching dynasty. Friuli became the base of power of Berengar I during his struggles for the throne of Italy between 888 and 924.
The march was transformed under his rule, its territory extended to Lake Garda, the capital moved to Verona, and a new March of Verona and Aquileia established in its place. The territory was now subjected to the Duchy of Bavaria, then to the Duchy of Carinthia, for more than a century.
On 3 April 1077, the Emperor Henry IV granted the county of Friuli, with ducal status, to Sigaerd, Patriarch of Aquileia. In the succeeding centuries, the patriarchate expanded its control over neighboring Trieste, Istria, Carinthia, Styria, and Cadore. The patriarchal state of Friuli was one of the best organized polities of the Italian Middle Ages. From the 12th century it possessed a parliament representing the communes as well as the nobility and the clergy. This institution only survived six centuries, remaining alive yet weak even during Venetian domination. It convened for the last time in 1805, when it was abolished by Napoleon Bonaparte. The Patriarch Marquard of Randeck (1365–1381) had gathered together and codified all the laws of Friuli and promulgated them as the Constitutiones Patriae Foriiulii ("Constitutions of the Country of Friuli"). Cividale del Friuli was seat of the Patriarchate until 1238, when the patriarch moved his seat to Udine, where he had a magnificent episcopal edifice constructed. Udine was so important that it in time became the institutional capital of Friuli.
Friuli