Old St. Paul’s, also titled Old Saint Paul’s: A Tale of the Plague and the Fire, is a novel by William Harrison Ainsworth serially published in The Sunday Times from 3 January 1841 to 26 December 1841.

The story of Old St. Paul’s is spread over six books which range between April 1665 and September 1666, culminating in the Great Fire of London.

Arthur Linfoot noted that he had ‘spent [the] afternoon on French and reading “Old St Paul’s”’ (presumably not all of it) in his diary entry of 20 November 1917 while stationed at Wallon Cappell.