St. Paul in Britain; or, The origin of British as opposed to papal Christianity is a book written by Richard Williams Morgan and published in 1861.

[4] The work suggests the early entry of Christianity into Britain by Paul the Apostle, Simon Zelotes and Joseph of Aramathea.

[1] History professor Joanne Pearson commented that "Morgan's lifetime saw both the heyday and the demise of the story in Wales" of an alleged early entry of Christianity, which began the year Morgan was born with works written by Bishop Thomas Burgess arguing that Paul the Apostle converted Britain to Christianity and ended with an essay by Vicar John Pryce which refuted the arguments for an early entry of Christianity and was written shortly before his death.

[2] The author Gerald Gardner had a copy of Morgan's book and used it as the basis for his writing on British Christianity.

[6] Edward Cardwell published a critical booklet on the topic in 1837 entitled The Supposed Visit of St Paul to Britain: a Lecture Delivered in the University of Oxford (Sermons, Volume 2), that predated Morgan's book.