The Great Apostasy is a concept within Christianity to describe a perception that mainstream Christian Churches have fallen away from the original faith founded by Jesus and promulgated through his Twelve Apostles.

Restorationism, also known as Restitutionism or Christian primitivism, is a religious perspective according to which the early beliefs and practices of the followers of Jesus were either lost or adulterated after his death and required a "restoration". It is a view that often "seeks to correct faults or deficiencies by appealing to the primitive church as normative model".