Eastern Christianity appeared in the region of Diocese of Chełm in the 10th century. After the Kiev Ruthenia had been baptised in 988 under Włodzimierz the Great, Christian missions reached the western part of the country. In 992 in Włodzimierz Wołyński the Orthodox bishopric was established, including the area between Wieprz and Bug rivers.
In one of the medieval historical resources dated 1072 there was mentioned Ioann, Bishop of Chełm, however this information cannot be confirmed. It is certain, however, that in 1205 there existed the Orthodox diocese in Uhrusk-upon-Bug under the bishop Joasaf. That was a period when at the territory of the Ruthenia there were many duchies, whose borders and sovereigns were constantly changing. The area of the today’s diocese had firstly been a part of Włodzimierz Duchy, which later divided into smaller units. In the twenties of the 13th century prince Daniel Halicki, one of the Włodzimierz the Great descendants, started to unite the Ruthenia. The Ruthenian lands with Kiev, Halicz and Włodzimierz were joined into Halicz- Włodzimierz Duchy, which became one of the biggest Central- Eastern European countries. Prince Daniel had built the town Chełm, which he later made the capital of the duchy. In 1223 (or 1240) he transferred the bishopric from Uhrusk to the new capital. He had also founded four Orthodox churches in Chełm, including the cathedral of The Theotokos on Chełm Mountain, which became the residence of bishops. Icon of the Mother of God of Chełm that had been brought from Constantinople to the Ruthenia in the 10th century was placed in the cathedral. Princes of Chełm and Chełm bishops were buried in that church.
Iwan, who came probably from Włodzimierz Wołyński, was the first bishop of Chełm. The diocese from the beginning of its existence was a part of Kiev metropolis that was subordinated to the Patriarch of Constantinople. The diocese included the area between Wieprz and Bug rivers – Chełm region as well as the areas beyond Bug river – Bełsk region. Bishops were titled as Bishops of Chełm and Bełsk. Southern Podlasie, which constitutes a north-eastern part of today’s diocese, belonged then to the Diocese of Włodzimierz.
After Prince Daniel’s death the duchy was divided and Chełm lost its great importance. Prince’s descendants were ruling in Chełm until the second part of the 14th c. when those areas became a part of Polish country. Then Poles started to settle down there and as a result the structure of The Catholic Church was developing. In 1358 or 1359 the Catholic bishopric was established in Chełm, according to the rule of establishing Catholic bishoprics in places where there had previously existed Orthodox bishoprics. However, at the beginning the Catholic bishopric was not very prominent as there were only few Catholic churches in Chełm region. During the 15th c. 29 new churches were built and Polish king Wladislaw Jagiełło (1386-1434) generously endowed the Catholic bishopric.
In 15th-16th c. the Orthodox Church was losing its rights and importance; e.g. in 1436 it was prohibited to build and renovate the Orthodox churches. The Orthodox people had limited access to get a post in the country's or cities’ authorities. Nevertheless the Orthodox Church was able to function in the country and not all restrictions were obeyed. At that time Chełm- Bełsk Diocese was quite developed. It was located on 22,000 km2 and included around 320 parishes. In Chełm itself there were 5 Orthodox churches. There existed also monasteries, among others in Chełm, Uhrusk and Stołpie that played an important role in the diocese.
The Union of Brest (1596) changed the situation of the Orthodox Church in Poland as most of the Orthodox bishops converted to the Catholic faith and accepted pope's authority over the church. Dionizy Zbirujski, Bishop of Chełm, among others, signed the Union. However majority of the people, in Chełm diocese as well, did not want to accept it. On the other hand, the king and the Catholic Church were supporting the Union. As a result, the Orthodox Church was declared as operating outside the law and Orthodox people were forced to accept the Union. The Orthodox churches and properties were confiscated, even if the Orthodox believers constituted the majority of the towns’ inhabitants. In Chełm, for instance, even though most of the Orthodox people resisted the Union, they did not have any church as all of them were taken over by the Uniats. The towns owned by the Orthodox noblemen were the only one where the churches were still Orthodox. In general, the Orthodox people were persecuted, churches were robbed, and priests were taken out from their parishes. Saint martyr Atanazy of Brest became a symbol of resistance to the Union.
The Orthodox Chełm- Bełsk Diocese was without the bishop as inhabitants did not longer acknowledge Bishop Dionizy because he had accepted the Union and the king did not want to agree to ordain a new bishop. Gedeon, Bishop of Lwow, a representative of Constantinople’s Patriarch, took the diocese under his protection. At that time the importance of some Orthodox monasteries and brotherhoods grew as they were opposing the Union. The oldest and the most prominent brotherhoods in the Diocese of Chełm were in: Krasnystaw (founded at the beginning of the 16th c.), Lublin (1586) and Zamość (1589) which in 1615 was granted stauropigial status, i.e. was under the direct jurisdiction of Patriarch of Constantinople.
In the year 1620 the authorities of the Orthodox Church in Poland were reestablished by Teofanes, Patriarch of Jerusalem, who, without the king’s knowledge, ordained in Kiev new bishops. New hierarchs, among them Paisjusz, Bishop of Chełm, were not accepted by the national authorities and could not work legally. Bishop Paisjusz was not allowed to enter the church as it belonged to the Uniats. He was ruling the diocese residing in St. Onufry Monastery in Jabłeczna, which then belonged to the Diocese of Włodzimierz.
In 1633 king Wladislaw IV agreed to give back some rights to the Orthodox Church. In April 1633 in Lwow Piotr Mohyla was ordained a new metropolitan of Kiev. However, the king did not agree to reestablish the diocese in Chełm and the inhabitants were given under the protection of bishop of Luck. The king also ordered to return some churches to the Orthodox people; however the Uniats' bishop strongly opposed it.
Persecution of the Orthodox Church became one of the reasons of Ukrainian Cossacks’ uprisings in the 17th century. The biggest uprising under Bohdan Chmielnicki’s command broke out in 1648. One of the Cossacks’ demands was to return all rights to the Orthodox Church and give back churches, many of which were located in the Diocese of Chełm. At the areas occupied by Cossacks, temples were returned to the Orthodox people. That was also the case of the Diocese in Chełm when in 1648 the army led by Chmielnicki invaded the region. After winning in August 1649 the battle in Zborów, under the signed treaty few Orthodox bishoprics (among others Diocese of Chełm) were reestablished and it was pledged that the churches Gould be returned. At the beginning of 1650 new Bishop Dionizy (Bałaban) started his rules in Chełm- Bełsk Diocese, and the cathedral in Chełm returned to the Orthodox people. However, in 1651 after Cossacks had lost the battle in Beresteczko, the cathedral in Chełm and many other Orthodox churches were again taken over by the Uniats. Those churches were returned not for long as in 1654 Cossacks and Russian armies invaded those regions (according to the treaty signed in Perejasław, under which Ukraine was incorporated into Russia).
In 1658 Cossack hetman Iwan Wyhowski made a new treaty (called Hadziacz treaty) with Polish Republic: great autonomy was to be granted to Ukraine, the Union was supposed to be terminated and freedom of religion was to be granted to the Orthodox people. The treaty also acknowledged the existence of Diocese in Chełm. However the treaty never came into force and after left-bank Ukraine was incorporated into Russia, the Orthodox Church in Polish Republic lost its important protector – the Cossacks. At that time, regardless of persecution, most of the churches in Chełm-Bełsk Diocese still belonged to the Orthodox people. However during the 17th and 18th centuries many churches and monasteries agreed to accept the Union. At the end of the 18th c. there were very few places at the west side of Bug river that remained Orthodox, and St. Onufry Monastery in Jabłeczna was one of those left.
At the end of the 18th c. as a result of Poland’s partitions western part of the Diocese of Chełm and Podlasie region were incorporated into Austrian Empire; and the eastern part of diocese – into Russia. At that time the part of Podlasie region that had previously belonged to Włodzimierz-Brest Diocese was joined with the Uniate Diocese of Chełm. The Orthodox people at Chełm and Podlasie regions were then under the jurisdiction of the Orthodox Metropolitan of Bukowina.
After the Napoleonic Wars, under the Congress of Vienna resolution (1815) those regions constituted a part of Polish Kingdom, which was ruled by Russian tsars. However, only at the end of the thirties the Orthodox churches were renovated as well as new one were build for Russian officials and soldiers also in the areas where there had not previously been any Orthodox people – in the western part of Lublin region. Local Orthodox parishes were ruled by bishops of Minsk and from 1834 by bishops of Warsaw.
In the 18th and 19th centuries many customs and traditions characteristic of Latin churches were introduced into the Uniate Church that is why it lost its eastern character. The language was being polonized even though the people were of Russian origin. In the first half of the 19th c. there were two major groups in the Uniate Church: supporters of the view that the Church should further assimilate with Roman-Catholic Church; and those who wanted the Church to go back to eastern tradition and to hault Polonization and Latinization. In the forties few villages in the southern part of Chełm region reconverted to the Orthodox faith, which was supported by the Russian authorities. In the sixties the authorities took steps towards delatinization of the Uniate Church what caused resistance among many Uniats, there were also cases of death.
In 1875 the Uniate Diocese of Chełm and the Orthodox Church were officially joined. Many of the Uniats did not want to return to the Orthodox faith so the Russian authorities victimized them to do so. The Diocese of Chełm was merged with the Diocese of Warsaw into one diocese seated in Warsaw. However at the same time in Chełm there had the residence bishop-curates with the title 'Bishop of Lublin'.
In 1905 tsar Nikolai II issued an imperial edict allowing to change the denomination. Approximately 150-180 thousand Uniats then converted themselves into the Roman- Catholics. In 1905 the Orthodox Diocese of Chełm was reestablished and Eulogiusz was chosen a new bishop. On the brink of the First World War there were 282 parishes, 5 monasteries and the seminary in the diocese; there existed diocesan museum and many other institutions as well as there were few periodicals published.
In the summer of 1915 the majority of the Orthodox people and many institutions, including the authorities of the Church, were transferred into Russia. The Diocese’ area was under German and Austrian occupation. The situation in the southern part of the diocese, which was under Austrian ruling, was very difficult for the Orthodox people and the churches were given by the authorities to the Roman-Catholics. Based on the treaty in Brest signed by Ukraine and central countries in February 1918, Chełm region and the southern part of Podlasie region were to be incorporated into Ukraine. However that was not realized and in 1918/1919 the area of the Diocese in Chełm became a part of the reestablished Poland and the Orthodox people could return to their homes.
However, the authorities and the society were prejudiced against the Orthodox Church, many churches and properties were seized and given to the Roman-Catholic Church. The number of the Orthodox parishes was limited, e.g. in 1925 there existed only 57 parishes and one monastery, and the Diocese in Chełm had been liquidated. The authorities intervened in the church life, imposed polonization, forced to follow new style (the Gregorian calendar) in the liturgical year and got rid of some priests. The peak of persecutions of the Orthodox Church at Chełm and Podlasie regions was in 1938, when more than 150 churches were destroyed.
During the Second World War the situation was also difficult. Germans, occupying Poland, agreed however to reestablish in 1940 Chełm-Podlasie Diocese and prominent Ukrainian professor Iwan Ohijenko became Archbishop Iłarion. Many parishes were then reestablished, the Seminary, museum and publishing house were created in Chełm. However, during the war and in the post-war period many believers and priests died.
After the war the communist authorities in Poland decided to expel the Orthodox Ukrainians. In 1944-1947 those inhabitants were sent to Ukraine as well as northern and western regions of Poland, which were gained after the war (Operation ‘Wisła’). At the Diocese of Chełm area very few Orthodox people were left and there were few parishes and one monastery (in Jabłeczna), and the diocese itself was soon liquidated. The Orthodox people returned home after 1956 and then the Orthodox Church was partly restored.
1989 was a breakthrough as the Orthodox diocese at this area was again reestablished, now as “Lublin-Chełm Diocese” under the leadership of Bishop Abel, and Lublin became his residence.