Christianity had a complicated relationship to slavery from the beginning. Many of the early Christians in the early centuries of the Church were slaves, including bishops, martyrs, evangelists and even popes. Celsus, a 2nd-century pagan, even mocked Christianity because religion was only suitable for women and slaves.
Throughout history, Christians were sometimes complicit in slavery and sometimes fought against it. The lives of these slaves, who became Catholic saints, shows how complex and nuanced this story really is. In 1766, he was born in Haiti as a house slave of the French aristocratic family Berard. At the age of 21, he experienced the slave revolt in Haiti, which was to become the Haitian revolution. The Berard family fled the country and took Toussaint to New York.
Toussaint stayed with the family in New York, even after losing their fortune. He became a famous hairdresser and designed fabulous hairstyles for the New York elite. [1
After the death of Ms. Berard, Toussaint was granted freedom and he married a Haitian. He supported many charities and was known for his generosity. He died in 1853.
Toussaint is a controversial saint. As a hero of the Catholics for his faith, he was a devout believer who attended the Daily Mass in St. Patrick's Cathedral for 66 years. Unfortunately, others in our time have a far more cynical opinion of him that he should have fought harder against slavery.
9 Saint Patrick
Saint Patrick is perhaps the most famous canonized ex-slave. Enslaved by the Irish, he became bishop of Armagh in Ireland and has the honor to convert the Irish people. His feast day on March 17 is still celebrated around the world.
Patrick was born into a Roman-British Christian family, but according to himself never had much time for the religion of his parents.  When he was 16, he was captured by Irish slavers. He was brought to Ireland and worked as a shepherd until he finally escaped. When he returned home, Patrick decided to become a priest.
After his later confessions Patrick heard the voice of the Irish, who called him back to evangelise them. He did just that and returned to convert the people who had enslaved him as a teenager. He fought slavery in Ireland and condemned the dreaded slave trader Coroticus.
8 Saint Seraphia
Saint Serapia was a Christian slave who lived in the 2nd century. The accounts of her life were written much later and the exact details are hard to determine. 
The story goes that she was born at the end of the first century in Antioch and with her parents fled to Rome. She sold herself into slavery and gave away all her possessions. Her lover was a Roman nobleman, Sabina, who was able to convert Serapia to Christianity.
At that time, being a Christian was illegal, and Serapia was tried and sentenced to death. A year later, Sabina was also killed when she was a Christian, and the two women were buried together.
In 425, on the site of her martyrdom, a church was dedicated to Saints Sabina and Serapina. Until the thirteenth century, the church, now known simply as Santa Sabina, increased the importance of St. Serapia. It became the international headquarters of the Dominican Order.
7 Saint Josephine Bakhita
Saint Josephine Bakhita was born around 1869 in Darfur, Sudan. She was captured by slavers at the age of nine and widely sold in the slave markets of Sudan. She was enslaved to a brutal family that beat her every day until she bleed and left scars for the rest of her life. 
Bakhita, as it was called, was sold to The Italian Deputy Callisto Legnani. The unrest in Sudan forced Legnani to return to Italy, and Josephine accompanied him. When they arrived in Italy in 1884, she was "sold" to a friend of the family, Turina Michieli from Venice. There in Venice she stayed with the Cannossian sisters for a few months while her "sweetheart" traveled.
When she returned, Bakhita refused to leave the monastery. She described the discovery of the love of God among the sisters. Finally, an Italian court stated that it had never been legally enslaved under English, Italian or Ethiopian law. Bakhita was free. She was baptized by the Patriarch of Venice, the future Pope Pius X, and joined as sister Josephine Fortuna the Cannossian sisters. She died in 1947 and was canonized in 2000.
6 The holy Isaac Jogues
The holy Isaac Jogues was a French missionary. He was born in 1607 and joined the Jesuits as a young man with zeal for the missions. In 1636 he traveled to the New World and was assigned to the First Nations of the Iroquois.
In 1642, Jogues traveled with a group of Christian hurons when they were attacked by members of the Mohawk nation. He was captured and tortured, beaten and his thumbs cut off. For two years he was in captivity and was only able to collect sticks because of his broken body. 
Eventually he managed to escape and he returned to France. There, the Pope granted him a special arrangement to celebrate the Mass without fingers and forefingers. After a few years, Jogues asked to return to New France. The relationship between the Jesuits and the Iroquois had only worsened and they were accused of bringing disease, hunger and drought. In 1646 Jogues was again attacked on October 18 with a tomahawk on his head and killed.
5 The Saints Exuperius and Zoe of Pamphylia
Another early church martyr of whom we know little is St. Exuperius. He, his wife St. Zoe and their two sons Cyriacus and Theodulus were martyred in the middle of the second century.
What makes them remarkable is that they were a family of slaves who were martyred. Their master ordered them to participate in pagan rituals, but they all rejected. In retaliation, they burned about 140 AD.  Your holiday is May 2nd.
4 Saint Raymond Nonnatus
Saint Raymond Nonnatus was a Catalan saint born in 1204. Nickname Nonnatus (Latin "not born") because he was born by caesarean section. He joined the Mercedarian Order, founded in 1218, with the specific purpose of releasing Christians who had been captured and enslaved by Moorish pirates in the Mediterranean.
He traveled to North Africa to acquit enslaved Christians with the Order's money. When he had no more money, he offered in return.  Nonnatus continued to preach as a prisoner, infuriating his captors. As a form of torture his lips are burned with a hot iron and his mouth closed with a padlock. He was eventually rescued, but died soon afterwards in 1240.
3 Saint Onesimus
Saint Onesimus is the only ex-slave to appear in the New Testament. He was the slave of Philemon, but ran away from him, became a Christian, and began to serve the apostle Paul. Paul wrote a short letter to his master, Philemon, asking him to return Onesimus without punishment, and even to release him, recognizing him as a brother in Christ of what Onesimus has done after the letter, he seems to be free. It may be the same Onesimus who accompanied Paul on his missionary journeys, calling Paul "Onesimus, our faithful and loving brother."
In a traditional account, Onesimus was ordained bishop of Ephesus and 19659004 Pope Saint Calixstus
Pope Saint Calixtus was a Roman slave born in the late second century. Condemned as a Christian, he was sentenced to forced labor in the mines of Sardinia. After his release, he returned to Rome and was ordained a deacon by Pope Zephrynius. In 217 he succeeded him as Bishop of Rome and Pope.
During his reign as pope, the church had its first counterweight when Hippolytus formed its own Christian community against Calixt. He believed Calixtus was too lenient towards sinners.
The Pope is listed as a martyr. Tradition has it that he was killed and thrown into a well. His body was saved and today the relics of the Holy Pope are in Santa Maria in Trastevere in Rome. 
1 Blessed Francisco de Paula Victor
Blessed Francisco de Paula Victor was born in Brazil in 1827 as a slave. He trained as a tailor, but always dreamed of becoming a priest. Victor was granted a special permit to attend the seminar. There, however, he was severely discriminated against and persecuted. In his first parish as an ordained priest, his parishioners refused to receive the sacrament from him because he was a black slave. He was able to win people over.  He established a large school for all students, regardless of their race or status.
Brazil finally abolished slavery in 1888. Father Victor died in 1905, and his church mourned for him. He was beatified in 2015 and is the first ex-slave priest to be on the way to canonization.
+ The process of canonization
The canonization is considered by the ruling Pope to be an infallible decree that a certain person is in heaven (Catholics believe that all men in heaven are saints). It is not thought that the process sends a person to heaven, but that she is certain that she is already there.
The reason? In order for the faithful to pray for the intercession of this person (it is generally frowned upon to publicly pray for the help of those who are not safe in heaven, but privately it is all right). The three steps of the process are Venerable, then Blessed, then Holy.
The above video is archival material of the arrival of (now revered) Pope Pius XII, who is carried up on his throne to proclaim the canonization for Pope Pius X. XVI. Came close to the restoration of many traditional pieces of papal garb. The same may be true if the present Pope is replaced by a more traditional one.
About the author: Laura McAlister is an Australian writer and history lover. She studied a M.Phil in Medieval Studies at Trinity College Dublin and a M.A in Theological Studies at the University of Notre Dame Australia. She lives in Sydney, Australia and loves to discuss Jane Austen, mystery and gender roles in tea and biscuits. She blogs at www.cravinggraces.com about prayer, perfectionism and the Catholic faith.