A first Bishop of Trent is recorded as a participant of the synod at Aquileia in 301.
The area was part of the Lombard Kingdom and the Kingdom of Italy, until the 951 campaign of German king Otto I against King Berengar II of Italy.
In 952 Berengar had to cede the March of Verona to Otto, who enfeoffed his younger brother Duke Henry I of Bavaria.
 
From 1004 Emperor Henry II the Saint and his successor Conrad II separated several smaller territories in the northeast of the Veronese march and granted them to the Trient diocese.
Originally a Bavarian fief, by 1027 the prince-bishopric was established, together with the similar Prince-Bishopric of Brixen.
The states were created to favor passage to Imperial armies across the Alps towards Italy along the two ancient roads, the Via Claudia-Augusta and the Via Altinate, entrusting the area to two bishops instead of often rebellious lay princes.

The prince-bishops were true Holy Roman Empire princes, and enjoyed the right to take part to Imperial diets.
The princes of Trento maintained a strong allegiance to the Emperor, even when the latter was excommunicated: this because they need his protection against the growing power of subjects like the counts of Tyrol, who controlled the area around Bozen, those of Eppan, and others.
In one of the attempts to reassure his temporal authority over these lesser but fierce nobles, the bishop Adelpreto was slaughtered at Arco, on September 20, 1172, by the lords of Castelbarco.
The supremacy of the prince-bishops of Trento and Brixen were however re-established by Emperor Frederick Barbarossa in 1179 and again by his son Henry VI of Hohenstaufen.
The bishop earned the right to have a coin of his own and to impose tolls.

The principate was reorganized and reformed by bishop Federico Wanga (1207–18), a relative of Emperor Otto IV.
Allied with the Bishop of Brixen and allowing wide estates to the Teutonic Knights he managed to thwart at all the nobles' strength, and recovered much of the territories lost in the past years.
In order to state in a definitive way his authority he also collected all the official documents certificating the bishop's authority in the so-called Book of St Vigilius (Codex Wangianus), Vigilius being the patron saint of Trento.
Moreover, Federico supported trading over the Adige way across the Alps, and made concessions to the middle class.
The drying of the valley allowed the area to become one of the most renowned of Italy for the production of wine.
The statute issued by Federico on June 19, 1208, is considered the most ancient official document concerning the Alps mining industry.
The city was encircled with a new line of walls and towers, and the building of the Cathedral was commenced.

The death of Wanga in the Holy Land, during a Crusade, stopped his reforms.
In 1236 Emperor Frederick II of Hohenstaufen deposed the bishops and ensured to himself the authority over the important military area of Trento, annexing it to the Mark of Treviso — the administration was entrusted to his faithful friend, Ezzelino III da Romano at Verona.

In the 13th century the Counts of Tyrol took advantage of the confused situation to carve out a conspicuous power as a Vogt for himself, much at the loss of the Bishops of Chur, Brixen, the Archbishopric of Salzburg and Trento itself.
Count Meinhard II of Tyrol (1258–1295), also Duke of Carinthia from 1286, totally subjected the bishops of Trento and Brixen under his power, and reorganized his new state along the more modern lines inspired to those of other Italian principalities.
In the 14th century, during the disputes between the rival emperors Charles IV of Luxembourg and Louis IV of Wittelsbach, the principality suffered several destructions and was temporarily again annexed to the latter's Bavarian territories.
The threat by Tyrol increased, when in 1363 Countess Margaret Maultasch ceded her lands to Rudolf IV of Austria from the mighty House of Habsburg.
A first Bishop of Trent is recorded as a participant of the synod at Aquileia in 301. The area was part of the Lombard Kingdom and the Kingdom of Italy, until the 951 campaign of German king Otto I against King Berengar II of Italy. In 952 Berengar had to cede the March of Verona to Otto, who enfeoffed his younger brother Duke Henry I of Bavaria.  
From 1004 Emperor Henry II the Saint and his successor Conrad II separated several smaller territories in the northeast of the Veronese march and granted them to the Trient diocese. Originally a Bavarian fief, by 1027 the prince-bishopric was established, together with the similar Prince-Bishopric of Brixen. The states were created to favor passage to Imperial armies across the Alps towards Italy along the two ancient roads, the Via Claudia-Augusta and the Via Altinate, entrusting the area to two bishops instead of often rebellious lay princes.
The prince-bishops were true Holy Roman Empire princes, and enjoyed the right to take part to Imperial diets. The princes of Trento maintained a strong allegiance to the Emperor, even when the latter was excommunicated: this because they need his protection against the growing power of subjects like the counts of Tyrol, who controlled the area around Bozen, those of Eppan, and others. In one of the attempts to reassure his temporal authority over these lesser but fierce nobles, the bishop Adelpreto was slaughtered at Arco, on September 20, 1172, by the lords of Castelbarco. The supremacy of the prince-bishops of Trento and Brixen were however re-established by Emperor Frederick Barbarossa in 1179 and again by his son Henry VI of Hohenstaufen. The bishop earned the right to have a coin of his own and to impose tolls.
The principate was reorganized and reformed by bishop Federico Wanga (1207–18), a relative of Emperor Otto IV. Allied with the Bishop of Brixen and allowing wide estates to the Teutonic Knights he managed to thwart at all the nobles' strength, and recovered much of the territories lost in the past years. In order to state in a definitive way his authority he also collected all the official documents certificating the bishop's authority in the so-called Book of St Vigilius (Codex Wangianus), Vigilius being the patron saint of Trento. Moreover, Federico supported trading over the Adige way across the Alps, and made concessions to the middle class. The drying of the valley allowed the area to become one of the most renowned of Italy for the production of wine. The statute issued by Federico on June 19, 1208, is considered the most ancient official document concerning the Alps mining industry. The city was encircled with a new line of walls and towers, and the building of the Cathedral was commenced.
The death of Wanga in the Holy Land, during a Crusade, stopped his reforms. In 1236 Emperor Frederick II of Hohenstaufen deposed the bishops and ensured to himself the authority over the important military area of Trento, annexing it to the Mark of Treviso — the administration was entrusted to his faithful friend, Ezzelino III da Romano at Verona.
In the 13th century the Counts of Tyrol took advantage of the confused situation to carve out a conspicuous power as a Vogt for himself, much at the loss of the Bishops of Chur, Brixen, the Archbishopric of Salzburg and Trento itself. Count Meinhard II of Tyrol (1258–1295), also Duke of Carinthia from 1286, totally subjected the bishops of Trento and Brixen under his power, and reorganized his new state along the more modern lines inspired to those of other Italian principalities. In the 14th century, during the disputes between the rival emperors Charles IV of Luxembourg and Louis IV of Wittelsbach, the principality suffered several destructions and was temporarily again annexed to the latter's Bavarian territories. The threat by Tyrol increased, when in 1363 Countess Margaret Maultasch ceded her lands to Rudolf IV of Austria from the mighty House of Habsburg.
Prince-Bishopric of Trent