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 1841. It is a historical romance that describes the events of the Great Plague of London and the Great Fire of London. It was the basis for the silent film Old St. Paul's.
In 1840, Ainsworth published Guy Fawkes and The Tower of London. When their serial publications were completed at the end of the year, Ainsworth began writing Old St. Paul's, A Tale of the Plague and the Fire. Ainsworth, in a letter to James Crossley 7 December 1840, wrote: "You told me that you have a second part of De Foe's History of the Plague. Pray bring this with you. I will take the greatest care of it, but it is quite necessary I should see it, as I commence a new Romance with the New Year, under the title of The Plague of London. If you have any other tract relating to the period, or to the Fire, I shall feel obliged by the loan of it".
Old St. Paul's ran in The Sunday Times from 3 January 1841 to 26 December 1841, and he was one of the first writers to appear in a national paper in such a form. Ainsworth was paid £1,000 for the work with control of the copyright. The work was later illustrated when it was published in a three volume set by Cunningham.
The story of Old St. Paul's is spread over six books that range between April 1665 and September 1666 and details the events of the grocer Stephen Bloundel's life. Part of the story deals with the pursuit of Amabel, Bloundel's daughter, by Leonard Holt, the grocer's apprentice, while she in turn pursues Maurice Wyvil. This happens while a plague hits London, and St Paul's Cathedral is turned into a place to house the sick. During the plague, London is filled with plague victims while many characters, including Anselm Chowles and Mother Malmaynes, go around killing and robbing the sick. Bloundel seals his house to avoid the plague. While this happens, Holt wanders alone in London and catches the plague, and Amabel Bloundel goes away to marry Wyvil.