Nicolaism (also Nicholaism, Nicolaitism, Nicolationism, or Nicolaitanism) was an early Christian sect mentioned twice in the Book of Revelation of the New Testament. The adherents were called Nicolaitans, Nicolaitanes, or Nicolaites. They were considered heretical by the mainstream early Christian Church. According to Revelation 2:6 and 15, they were known in the cities of Ephesus and Pergamum. In this chapter, the church at Ephesus is endorsed for "[hating] the works of the Nicolaites, which I also hate"; and the church in Pergamos is rebuked: "So thou hast also some [worshiping in their midst] who hold the teaching of the Nicolaites".
Several of the early Church Fathers mentioned this group, including Irenaeus, Tertullian, Clement of Alexandria, Hippolytus, Epiphanius, and Theodoret, stating that Nicolas the Deacon, one of the Seven Deacons, was the author of the heresy and the sect.
The New Testament mentions the Nicolaites in the second chapter of the Book of Revelation.
Yet this is to your credit [the church of Ephesus]: you hate the works of the Nicolaitans, which I [Jesus] also hate.
But I have a few things against you [the church of Pergamos]: you have some there who hold to the teaching of Balaam, who taught Balak to put a stumbling block before the people of Israel, so that they would eat food sacrificed to idols and practice fornication. So you also have some who hold to the teaching of the Nicolaitans. Repent then. If not, I will come to you soon and make war against them with the sword of my mouth.
The last Western Church Father was Isidore of Seville, who finished the Etymologies, in the year 636 AD. In Book VIII titled "The Church and sects (De ecclesia et secta)" he wrote, "The Nicolaites (Nicolaita) are so called from Nicolaus, deacon of the church of Jerusalem, who, along with Stephen and the others, was ordained by Peter. He abandoned his wife because of her beauty, so that whoever wanted to might enjoy her; the practice turned into debauchery, with partners being exchanged in turn.