The exact date of his birth is unknown.
Most probably, he joined Methodius as a young man following him later to the monastery on Mysian Olympus.
According to his hagiography by Theophylact of Ohrid, Clement knew the life of Methodius like no other.
That is why most scholars think he was born in the Byzantine Empire in the territory where Methodius served during his political career, i.e. that he was a Slav from Southern Macedonia.
This gives rise to some researchers to indicate the area of Thessaloniki as the possible place of birth of Clement.
According to others, the area of Southern Macedonia, including the northern approach to Thessaloniki, where he maybe was born, was then part of the First Bulgarian Empire.
Most of Macedonia became part of Bulgaria in 830s and in 840s, i.e when Clement was born.
The Short Life of St. Clement by Theophylact of Ohrid testifies to his Slavic origin, calling him "the first bishop in the Bulgarian language," while The Ohrid Legend written by Demetrios Chomatenos calls him a Bulgarian, who was born somewhere in Macedonia.
Because of that, some scholars label him a Bulgarian Slav, while Dimitri Obolensky calls Clement a Slav inhabitant of the Kingdom of Bulgaria.
A fringe view on his origin postulates that Clement was born in Great Moravia.
This view is based on the lexicographical analysis of Clement's works.

Clement participated in the mission of Cyril and Methodius to Great Moravia.
In 867 or 868 he became a priest in Rome, ordained along with two other disciples of Cyril and Methodius, Saint Gorazd and Saint Naum, by bishops Formosus and Gauderic.
After the death of Cyril, Clement accompanied Methodius on his journey from Rome to Pannonia and Great Moravia.
After the death of Methodius himself in 885, Clement headed the struggle against the German clergy in Great Moravia along with Gorazd.
After spending some time in jail, he was expelled from Great Moravia and in 885 or 886 reached Belgrade, then in the borders of Bulgaria together with Naum of Preslav, Angelarius and possibly Gorazd (according to other sources, Gorazd was already dead by that time).
Thereafter, the four of them were sent to the Bulgarian capital of Pliska where they were commissioned by Boris I of Bulgaria to instruct the future clergy of the state in the Old Slavonic language.

After the adoption of Christianity in 865, religious ceremonies in Bulgaria were conducted in Greek by clergy sent from the Byzantine Empire.
Fearing growing Byzantine influence and weakening of the state, Boris viewed the adoption of the Old Slavonic language as a way to preserve the political independence and stability of Bulgaria.
With a view thereto, Boris made arrangements for the establishment of two literary academies where theology was to be taught in the Slavonic language.
The first of the schools was to be founded in the capital, Pliska, and the second in the region of Kutmichevitsa.

According to his hagiography by Theophylact of Ohrid, while Naum stayed in Pliska working on the foundation of the Pliska Literary School, Clement was commissioned by Boris I to organise the teaching of theology to future clergymen in Old Church Slavonic in the southwestern part of the Bulgarian Empire, in the region then known as Kutmichevitsa.
For a period of seven years (between 886 and 893) Clement taught some 3,500 disciples in the Slavonic language and the Glagolitic alphabet.
At that time, Clement translated Christian literature into Old Church Slavonic, and in this way, he and his co-workers laid the foundations of the Bulgarian Orthodox Church.
In 893 he was ordained archbishop of Drembica, Velika (bishopric).
Upon his death in 916 he was buried in his monastery, Saint Panteleimon, in Ohrid.
Soon after he was canonized as a saint by the Bulgarian Orthodox Church.

The development of Old Church Slavonic literacy had the effect of preventing the assimilation of the South Slavs into neighbouring Byzantine culture, which promoted the formation of a distinct Bulgarian identity in the Empire.
During the first quarter of the 10th century, the ethnony
The exact date of his birth is unknown. Most probably, he joined Methodius as a young man following him later to the monastery on Mysian Olympus. According to his hagiography by Theophylact of Ohrid, Clement knew the life of Methodius like no other. That is why most scholars think he was born in the Byzantine Empire in the territory where Methodius served during his political career, i.e. that he was a Slav from Southern Macedonia. This gives rise to some researchers to indicate the area of Thessaloniki as the possible place of birth of Clement. According to others, the area of Southern Macedonia, including the northern approach to Thessaloniki, where he maybe was born, was then part of the First Bulgarian Empire. Most of Macedonia became part of Bulgaria in 830s and in 840s, i.e when Clement was born. The Short Life of St. Clement by Theophylact of Ohrid testifies to his Slavic origin, calling him "the first bishop in the Bulgarian language," while The Ohrid Legend written by Demetrios Chomatenos calls him a Bulgarian, who was born somewhere in Macedonia. Because of that, some scholars label him a Bulgarian Slav, while Dimitri Obolensky calls Clement a Slav inhabitant of the Kingdom of Bulgaria. A fringe view on his origin postulates that Clement was born in Great Moravia. This view is based on the lexicographical analysis of Clement's works.
Clement participated in the mission of Cyril and Methodius to Great Moravia. In 867 or 868 he became a priest in Rome, ordained along with two other disciples of Cyril and Methodius, Saint Gorazd and Saint Naum, by bishops Formosus and Gauderic. After the death of Cyril, Clement accompanied Methodius on his journey from Rome to Pannonia and Great Moravia. After the death of Methodius himself in 885, Clement headed the struggle against the German clergy in Great Moravia along with Gorazd. After spending some time in jail, he was expelled from Great Moravia and in 885 or 886 reached Belgrade, then in the borders of Bulgaria together with Naum of Preslav, Angelarius and possibly Gorazd (according to other sources, Gorazd was already dead by that time). Thereafter, the four of them were sent to the Bulgarian capital of Pliska where they were commissioned by Boris I of Bulgaria to instruct the future clergy of the state in the Old Slavonic language.
After the adoption of Christianity in 865, religious ceremonies in Bulgaria were conducted in Greek by clergy sent from the Byzantine Empire. Fearing growing Byzantine influence and weakening of the state, Boris viewed the adoption of the Old Slavonic language as a way to preserve the political independence and stability of Bulgaria. With a view thereto, Boris made arrangements for the establishment of two literary academies where theology was to be taught in the Slavonic language. The first of the schools was to be founded in the capital, Pliska, and the second in the region of Kutmichevitsa.
According to his hagiography by Theophylact of Ohrid, while Naum stayed in Pliska working on the foundation of the Pliska Literary School, Clement was commissioned by Boris I to organise the teaching of theology to future clergymen in Old Church Slavonic in the southwestern part of the Bulgarian Empire, in the region then known as Kutmichevitsa. For a period of seven years (between 886 and 893) Clement taught some 3,500 disciples in the Slavonic language and the Glagolitic alphabet. At that time, Clement translated Christian literature into Old Church Slavonic, and in this way, he and his co-workers laid the foundations of the Bulgarian Orthodox Church. In 893 he was ordained archbishop of Drembica, Velika (bishopric). Upon his death in 916 he was buried in his monastery, Saint Panteleimon, in Ohrid. Soon after he was canonized as a saint by the Bulgarian Orthodox Church. 
The development of Old Church Slavonic literacy had the effect of preventing the assimilation of the South Slavs into neighbouring Byzantine culture, which promoted the formation of a distinct Bulgarian identity in the Empire. During the first quarter of the 10th century, the ethnony
Clement of Ohrid