They are sometimes identified as the group called "Nazorei" by Filaster, and were certainly one of the earliest key Gnostic sects. These days the term is most commonly used to refer to various sects of messianic Jews. Many of the original Nasoraeans became Christians and the word in modern Hebrew is applied derogatively to Christians in general.
It appears that the Νασαραίοι were originally composed at least partly of Jews (viz., Israeli-Samaritans) beginning long before the Christian Era, whose anti-Torah teachings may have had some gnostic leanings. The sect was apparently centered in the areas of Coele-Syria, Galilee and Samaria (essentially corresponding to the long-defunct state of Northern Israel).
The Orthodox Church Father Epiphanius writes: "there were Nasoraeans amongst the Jews before the time of Christ. They were said to have rejected temple sacrifice and the Torah, but adhered to other Jewish practice. They are described as being vegetarian. Epiphanius says it was unlawful for them to eat meat or make sacrifices. According to him they were Jews only by nationality who lived in Gilead, Basham, and the Transjordan. They revered Moses but, unlike the pro-Torah Nazoraeans, believed he had received different laws from those accredited to him.
Following the teachings of the Prophets above the Priestly rituals, they are considered Minim (heretics) by the Pharisee-derived Rabbinic Judaism in the Mishnah. They were members of a non-priestly congregation that counted Jeremiah as an early leader five centuries before. Key teachings are that sacrifices were created by the priesthood to feed the Priests, and are not in accord with God's Law. E. S. Drower surmises that the Nasoraean hatred for Jews originated during a period in which they were in close contact with orthodox Jewry, and when the latter was able to exercise authority over them.
The famous Notzrim of the pre-Christian era (in existence during the reign of Alexander Jannaeus) included a rebellious student mentioned in the Baraitas as "Yeshu Ha-Notzri". Some fringe scholars identify this individual as the Christian Jesus of Nazareth, although the identification has been contested, as Yeshu ha-Notzri is depicted as living circa 100 BCE.
The Notzri movement was particularly popular with the Samaritan Jews. While the Pharisees were waiting for a messiah who would be a descendant of David, the Samaritan messiah would restore the northern kingdom of Israel. The Samaritans emphasized their partial descent from the tribes of Ephraim and Manasseh and thereby from the Joseph of the Torah. They considered themselves the B'nei Yoseph (i.e. "sons of Joseph").
The Mandaeans, who consider themselves successors of the pre-Christian Notzrim, claim John the Baptist as a member (and onetime leader) of their sect; the River Jordan is a central feature of their doctrine of baptism. The term Mandaii itself may be the Aramaic/Mandaean equivalent of the Greek gnosis ("knowledge"). Besides the Mandaeans, they have frequently been connected with groups known as Naaseni, Naasenians, Naassenes.
According to a Mandaean manuscript, the Haran Gawaita, John the Baptist is baptized, initiated, and educated by the patron of the Nasirutha ("secret knowledge") Anus or Anus-’uthra, the hierophant of the sect. This research was conducted by the Oxford scholar, and specialist on the Nasoraeans, Dr. E. S. Drower, who concedes, however, that John’s name may have been inserted at a later date (it appears as Yahia, which is Arabic, not Aramaic). Drower also asserts that the Church Fathers Hippolytus and Eusebius describe Simon Magus, the Samaritan sorcerer of biblical fame (Acts 8:9ff), as a Nasoraean and a disciple of John the Baptist. The author of the pseudo-Clementine Homilies (Bk. II, xxiii-xxiv), also describes Simon Magus as a disciple of John the Baptist and a Nasoraean. The Homilies also state that the immediate successor to John was another Samaritan named Dositheus, elected as leader because Simon happened to be in Egypt at the time of the martyrdom of the Baptist. Homily (Bk II, xxiv) recounts that when Simon returned from Egypt, the two quarreled: Simon’s authority was proved by miracles; thus Dositheus ceded his position as head of the sect and became Simon’s pupil.
As a result of efforts to bring the sect back into the folds of Judaism they also disparaged the Christian books as fiction, regarding Jesus as the literary invention (mšiha kdaba) of Paul of Tarsus, but eventually they emerged towards the end of the 1st century as the Mandaeans though others actually managed to shape the anti-Torah development of Pauline Christianities like Marcionism.
In Arabic they were known as Nasara (نصارى).