The Diocese of Pontus was a diocese

Roman diocese

A Roman or civil diocese was one of the administrative divisions of the later Roman Empire, starting with the Tetrarchy. It formed the intermediate level of government, grouping several provinces and being in turn subordinated to a praetorian prefecture....

 of the later Roman Empire

Roman Empire

The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

, incorporating the provinces of northern and northeastern Asia Minor

Asia Minor

Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

 up to the border with the Sassanid Empire

Sassanid Empire

The Sassanid Empire , known to its inhabitants as Ērānshahr and Ērān in Middle Persian and resulting in the New Persian terms Iranshahr and Iran , was the last pre-Islamic Persian Empire, ruled by the Sasanian Dynasty from 224 to 651...

 in Armenia. The diocese was established after the reforms of Diocletian

Diocletian

Diocletian |latinized]] upon his accession to Diocletian . c. 22 December 244  – 3 December 311), was a Roman Emperor from 284 to 305....

, and its vicarius

Vicarius

Vicarius is a Latin word, meaning substitute or deputy. It is the root and origin of the English word "vicar" and cognate to the Persian word most familiar in the variant vizier....

, headquartered at Amaseia, was subordinate to the Praetorian prefecture of the East

Praetorian prefecture of the East

The praetorian prefecture of the East or of Oriens was one of four large praetorian prefectures into which the Late Roman Empire was divided...

. Its military forces, facing the Sassanid threat, were commanded by the dux Ponti et Armeniae until the middle of the 5th century, and by two separate duces afterwards, until Justinian I

Justinian I

Justinian I ; , ; 483– 13 or 14 November 565), commonly known as Justinian the Great, was Byzantine Emperor from 527 to 565. During his reign, Justinian sought to revive the Empire's greatness and reconquer the lost western half of the classical Roman Empire.One of the most important figures of...

 instituted a new magister militum

Magister militum

Magister militum was a top-level military command used in the later Roman Empire, dating from the reign of Constantine. Used alone, the term referred to the senior military officer of the Empire...

 per Armeniam for the Armenian frontier. Justinian's reforms also abolished the diocese in 535, and its vicar was made into the governor of Galatia I. The results however were not satisfactory, and the diocese was reestablished in 548, continuing to function until replaced by the themata of Armeniakon and Opsikion

Opsikion

The Opsician Theme or simply Opsikion was a Byzantine theme located in northwestern Asia Minor . Created from the imperial retinue army, the Opsikion was the largest and most prestigious of the early themes, being located closest to Constantinople...

 in the later 7th century.
On the north east shore of the Black Sea, the cities Nitike

Gagra

Gagra is a town in Abkhazia, Georgia’s breakaway republic, sprawling for 5 km on the northeast coast of the Black Sea, at the foot of the Caucasus Mountains...

, Pitiyus, and Dioscurias

Sukhumi

Sukhumi is the capital of Abkhazia, a disputed region on the Black Sea coast. The city suffered heavily during the Georgian-Abkhaz conflict in the early 1990s.-Naming:...

 were part of the diocese until the 7th century.
The diocese included 12 provinces: Bithynia

Bithynia

Bithynia was an ancient region, kingdom and Roman province in the northwest of Asia Minor, adjoining the Propontis, the Thracian Bosporus and the Euxine .-Description:...

, Honorias

Honorias

Honorias was a late Roman province encompassing parts of Bithynia and Paphlagonia in Asia Minor . Its capital was Claudiopolis , and its governor was of the rank of praeses....

, Paphlagonia

Paphlagonia

Paphlagonia was an ancient area on the Black Sea coast of north central Anatolia, situated between Bithynia to the west and Pontus to the east, and separated from Phrygia by a prolongation to the east of the Bithynian Olympus...

, Helenopontus, Pontus Polemoniacus, Galatia I

Galatia

Ancient Galatia was an area in the highlands of central Anatolia in modern Turkey. Galatia was named for the immigrant Gauls from Thrace , who settled here and became its ruling caste in the 3rd century BC, following the Gallic invasion of the Balkans in 279 BC. It has been called the "Gallia" of...

 and Galatia II (Salutaris)

Galatia

Ancient Galatia was an area in the highlands of central Anatolia in modern Turkey. Galatia was named for the immigrant Gauls from Thrace , who settled here and became its ruling caste in the 3rd century BC, following the Gallic invasion of the Balkans in 279 BC. It has been called the "Gallia" of...

, Cappadocia I

Cappadocia

Cappadocia is a historical region in Central Anatolia, largely in Nevşehir Province.In the time of Herodotus, the Cappadocians were reported as occupying the whole region from Mount Taurus to the vicinity of the Euxine...

 and Cappadocia II

Cappadocia

Cappadocia is a historical region in Central Anatolia, largely in Nevşehir Province.In the time of Herodotus, the Cappadocians were reported as occupying the whole region from Mount Taurus to the vicinity of the Euxine...

, Armenia I

Roman Armenia

From the end of the 1st century BC onwards, Armenia was, in part or whole, subject to the Roman Empire and its successor, the East Roman or Byzantine Empire...

, Armenia II

Roman Armenia

From the end of the 1st century BC onwards, Armenia was, in part or whole, subject to the Roman Empire and its successor, the East Roman or Byzantine Empire...

, Armenia Maior

Roman Armenia

From the end of the 1st century BC onwards, Armenia was, in part or whole, subject to the Roman Empire and its successor, the East Roman or Byzantine Empire...

 and the autonomous Armenian principalities (Satrapiae) in the area of Sophene

Sophene

Sophene , or ) was a province of the Armenian Kingdom and of the Roman Empire, located in the south-west of the kingdom. It currently lies in modern-day southeastern Turkey....

.