Pope Clement I, also known as Saint Clement of Rome, is listed by Irenaeus and Tertullian as Bishop of Rome, holding office from 88 to his death in 99. He is considered to be the first Apostolic Father of the Church, one of the three chief ones together with Polycarp and Ignatius of Antioch. 

Few details are known about Clement's life. Clement was said to have been consecrated by Peter, and he is known to have been a leading member of the church in Rome in the late 1st century. Early church lists place him as the second or third bishop of Rome after Peter. The Liber Pontificalis states that Clement died in Greece in the third year of Emperor Trajan's reign, or 101 AD.

Clement's only genuine extant writing is his letter to the church at Corinth (1 Clement) in response to a dispute in which certain presbyters of the Corinthian church had been deposed. He asserted the authority of the presbyters as rulers of the church on the ground that the Apostles had appointed such.  His letter, which is one of the oldest extant Christian documents outside the New Testament, was read in church, along with other epistles, some of which later became part of the Christian canon. These works were the first to affirm the apostolic authority of the clergy.  A second epistle, 2 Clement, was attributed to Clement, although recent scholarship suggests it to be a homily by another author.

Source: https://en.wikipedia.org/wiki/Pope_Clement_I

                                            St. Clement of Rome - c. 96 A.D.
First Epistle