Pope St. Eleutherius was a Greek, son of Habundius, born in Nicopolis, part of what is now Greece, some time after 100 AD. His name means “frank, honest, free-spirited”. Whether that is his real name or a description of the man is unknown. Eleutherius was Bishop of Rome from about 175 to May 24, 189 AD. It is said that he was martyred at that time.
Eleutherius, according to Hegesippus, the first Christian writer, was a deacon under Pope St. Anicetus and he stayed on after the death of that pope (c. 166). He succeeded Pope St. Soter and was influential during the reigns of Marcus Aurelius (d. 180) and his son Commadus (d. 192). Marcus Aurelius was fairly tolerant of Christians, although he was a pagan. But there were a number of prefects who took matters into their own hands and had local persecutions.
The biggest problem Eleutherius had to face was the continuing problem of the Montanists, also known as the “New Prophecy” and the Marcionists. These were groups of people who described themselves as Christians but tended to claim that the Holy Spirit was directing them to do and say things not adopted by the orthodox church. In many ways, they were similar to the Pentacostalists of today. However, with their fasting and ascetic ways, it was difficult to piece together whether they were actually heretical or not. The most embarrassing activities they held were their large public displays of ecstactic prophesying.
In 177, Eleutherius received a letter from the Church at Lyon, France, asking him to consider carefully the Marcionists, to show mercy but to not compromise in his dealing. The letter was delivered by the deacon, Ireneus, who shortly became the bishop of Lyon. It appears that either Eleutherius or his successor, Victor, actually wrote letters of support for this group, but recalled the letters based on further information.
An example of their displays is thus: “‘And he [Montanus] became beside himself, and being suddenly in a sort of frenzy and ecstasy, he raved, and began to babble and utter strange things, prophesying in a manner contrary to the constant custom of the Church handed down by tradition from the beginning.’ The Montanist prophets did not speak as messengers of God but were described as possessed by God while being unable to resist.[15] A prophetic utterance by Montanus described this possessed state: ‘Lo, the man is as a lyre, and I fly over him as a pick. The man sleepeth, while I watch.'” (from Wikipedia)
Due to the hesitancy on the part of the Roman Church, Tertullian came out in favor of the New Prophecy in 205, yet never converted. Meanwhile, many of the bishops in Asia Minor, where the heresy began, were totally against the sect early on. They had synods and wrote letters, disclaiming the followers. Eventually, the followers of Montanus claimed that he, himself was the Holy Spirit, the Paraclete, sent from Jesus to guide and direct the Church. That was the beginning of the end for this heresy.
Some references say he was martyred, others that he died a natural death. In either case, Pope Eleutherius was buried on Vatican Hill, near other popes. They were moved to the Church of Saint Susanna in 1591, at the request of Camilla Peretti, sister of Pope Sixtus V.

St. Eleutherius, pray for us.