St. Cletus was the third bishop of Rome, and succeeded St. Linus, which circumstance alone shows his eminent virtue among the first disciples of St. Peter in the West. He sat twelve years, from 76 to 89. The canon of the Roman mass, (which Bossuet and all others agree to be of primitive antiquity,) Bede, and other Martyrologists, style him a martyr. He was buried near St. Linus, on the Vatican, and his relics still remain in that church.
How do we know he was pope?
Like St. Linus before him, St. Cletus is identified by St. Irenaeus in his work Adversus haeresis (“Against Heresy”).
Give me the scoop on Cletus.
Pope St. Cletus was pope for 12 years. Early Church writers sometimes used more than one name to identify him — Cletus, Anacletus, or Anencletus — perhaps like one today would use “Jimmy” and “James” interchangeably for the same person. His feast day is celebrated on April 26, and he is traditionally remembered as having been martyred for the faith.
What was he known for?
The tradition of the Church says that St. Cletus was known for ordaining 25 priests during his rule, and was buried near St. Peter in Rome after his death. You can hear his name mentioned in the Roman Canon at Mass between “Linus” and “Clement”.
What else was going on in the world at the time?
Right around the beginning of St. Cletus’ papacy, the cities of Pompeii and Herculaneum were destroyed and buried after the eruption of Mt. Vesuvius (79 A.D.).