The term proto-orthodox Christianity or proto-orthodoxy describes the early Christian movement that was the precursor of Christian orthodoxy. Older literature often referred to the group as "early Catholic" in the sense that their views were the closest to those of the more organized Catholic Church of the 4th and 5th centuries. The term "proto-orthodox" was coined by Bentley Layton, but is often attributed to New Testament scholar Bart D. Ehrman, who has popularized the term by using it in books for a non-academic audience. Ehrman argues that when this group became prominent by the end of the third century, it "stifled its opposition, it claimed that its views had always been the majority position and that its rivals were, and always had been, 'heretics', who willfully 'chose' to reject the 'true belief'."

Gnosticism is a collection of religious ideas and systems that coalesced in the late 1st century AD among Jewish and early Christian sects. These various groups emphasized personal spiritual knowledge (gnosis) above the proto-orthodox teachings, traditions, and authority of religious institutions.