The Athinganoi (Ancient Greek: Ἀθίγγανοι, singular Athinganos, Ἀθίγγανος, Atsinganoi), were a Manichean sect regarded as Judaizing heretics who lived in Phrygia and Lycaonia but were neither Hebrews nor Gentiles. They kept the Sabbath, but were not circumcised. They were Shomer nagia. Other sources mentioned that the Athinganoi was Simonians, and have nothing to do with the Manichean or Paulinic sect, and settled in the year of the East–West Schism in 1054 at Byzantium, and married Byzantine women, adopted Greek Orthodox Christianity and later assimilated in Slavic and Greek Population. In some studies the Athinganoi are described as remnants of the Indo-Greeks who left India in 400 AD at the time of Migration period.
The etymology of the word is not certain, but a common determination is a derivation in Greek for "(the) untouchables" (compare Indian Chandala, dalit), derived from a privative alpha prefix and the verb thingano (θιγγάνειν, thinganein, "to touch"). The Manichean sect is mentioned in Soghdian sources.
The name Athinganoi, a later variant form of which is Atsinganoi (ἀτσίγγανοι), came to be associated with the Romani people who first appeared in the Byzantine Empire at the time. Atsinganoi is the root word for "cigano", "çingene", "cigány", "zigeuner", "tzigan", "țigan", and "zingaro", words used to describe members of the Romani people in various European languages. Today many of these words are still used in a derogatory sense, albeit others are the most common exonym for them in a given language. The idea of Roma as sorcerers also plays a part in the apparent confusion between the Atzinganos (the Roma), and the Athinganoi.
The exact relationship between the Athinganoi and the Romani people remains uncertain. Historians, such as Rochow, have suggested three different explanations for the association:
An earlier, and probably quite distinct, sect with the same name is refuted by Marcus Eremita, who seems to have been a disciple of St. John Chrysostom.
They were regarded as Judaizing Heretics. About AD 600, Timotheus, Presbyter of Constantinople, in his book De receptione Haereticorum adds at the end of his list of heretics who need rebaptism the Mandopolini, "now called Athingani. They live in Phrygia, and are neither Hebrews nor Gentiles. They keep the Sabbath, but are not circumcised. They will not touch any man. If food is offered to them, they ask for it to be placed on the ground; then they come and take it. They give to others with the same precautions".