Pope Anicetus was the eleventh bishop of Rome from c. 157 to his death in April 168. According to the Annuario Pontificio, the start of his papacy may have been 153. Anicetus actively opposed Gnosticism and Marcionism. He welcomed Polycarp of Smyrna to Rome to discuss the Easter controversy.
According to Irenaeus, it was during his pontificate that the aged Polycarp of Smyrna, a disciple of John the Evangelist, visited Rome to discuss the celebration of Pasch with Anicetus. Polycarp and his Church of Smyrna celebrated the crucifixion on the fourteenth day of Nisan, which coincides with Pesach (or Passover) regardless of which day of the week upon this date fell, while the Roman Church celebrated the Pasch on Sunday—the weekday of Jesus's resurrection. The two did not agree on a common date, but Anicetus conceded to Polycarp and the Church of Smyrna the ability to retain the date to which they were accustomed. The controversy was to grow heated in the following centuries.
Anicetus actively opposed the Gnostics and Marcionism. The Liber Pontificalis records that Anicetus decreed that priests are not allowed to have long hair (perhaps because the Gnostics wore long hair).
According to church tradition, Anicetus suffered martyrdom during the reign of Emperor Lucius Verus, but there are no historical grounds for this account. 16, 17 and 20 April are all cited as the date of his death, but 20 April is currently celebrated as his feast day. Before 1970, the date chosen was 17 April. The Liber Pontificalis states he was buried in the cemetery of Callistus.