History credits the English-born Roman Catholic missionary with bringing a 'nominal' form of Christianity to Ireland during circa 5th century AD. Here it is said he encountered the pagan 'Irish gods' (Celtic and Druid) which had bonfires in their honor and other symbols which Patrick is said to have adopted these to Easter celebrations, the Irish cross and some believe he used the shamrock to attempt to explain the Trinity.
History on the other hand has documents indicating that the Apostle James visited Ireland centuries before Patrick, preaching the gospel of the 'Good News' that Jesus gave His new church and disciples. Other historical documents indicate that Simon Peter, Simon Zelotes, Paul and others brought the original Christianity of Jesus to these European Western Isles in the 1st Century - about 400 years before Patrick brought his understanding.
Lastly, long before the Apostles brought the true gospel to Ireland, some language scholars argue the term 'Iberia' for Spain to be a variation of 'Hebrew' which these (Celts and the Scythians) believe migrated via the Lost Ten Tribes through the Caucasus Mountains to Western Europe and eventually the Isles. Later the Anglos and Saxons (possibly other Lost Tribe groups) came and settled in England primarily.
Practically every religion under the sun. There have been converts from the heretical sects such as protestants (I was baptized Methodist and raised Lutheran), Aztecs, Roman paganism, witchcraft, Druid, Hindu, Voodoo, you name it, the Catholic Church has been there to evangelize.
It depends on what time in Celtic history you are talking about. Broadly, very broadly, before Romans became Christians and then brought Christianity to the Celts, they practiced their native Pagan religion(s). They have many gods, and it appears that for many, if not all Celts, Druids were their priests. During and after Roman colonization, Christianity spread until it became the dominant religion among the remaining Celtic peoples.
Celtic religion started before Jesus had even come, they have been around forever, but the longer they go on the more they change and are forgotten.
Islam
None!
offshoot of judaism
Judaism and Christianity.
the Romans religion was Christianity
Protestant Christianity
Wikipedia: "The Celts had an indigenous polytheisticreligion and culture." "Polytheism is the belief in or worship of multiple deities, such as gods and goddesses." "While the regions under Roman rule adopted Christianity along with the rest of the Roman Empire, unconquered areas of Ireland and Scotland moved from Celtic polytheism to Celtic Christianity in the fifth century AD." "Celtic Christianity, or Insular Christianity (sometimes called the Celtic Church or the British Church or Irish Church) broadly refers to the Early Medieval Christian practice that developed in Britain and Ireland before and during the post-Roman period, when Germanic invasions sharply reduced contact between the broadly Celtic populations of Britons and Irish with Christians on the Continent until their subsequent conversion in the 5th and 6th centuries."
Greco-Roman Paganism/Polytheism.
Jesus was a practicing Jew.
roman catholicANSWER 2:Before Christianity came to the British Isles, Druids were predominant. They worshipped nature.ANSWER 3:During the Iron Age, the original religion of the land now known as England was Celtic polytheism. It was followed by Roman polytheism which outlawed the Druids. Christianity wasn't introduced into England until the Third Century.