Harry Potter and the Methods of Rationality is an alternate universe Harry Potter fanfiction written by Eliezer Yudkowsky, an AI researcher and decision theorist at the Singularity Institute for Artificial Intelligence. The story focuses on a Harry Potter who enters Hogwarts after having been raised with an Aunt Petunia who married a scientist. The fanfiction is known for possibly being the most reviewed Harry Potter fanfiction, with over 20,000 reviews on Fanfiction.net as of 29 June, 2013.
The fanfiction's official website can be found here. It features a mirror of the fanfiction, as well as a cover artwork and links to PDF, podcast and other versions. The site also contains notes from the author, background on scientific concepts featured within the series, fanart and an option for update notifications.
Harry Potter has lived for 11 years with the Evans-Verres - Petunia and her scientist husband Professor Michael, reasonably happy but unaware of magic. One day, he receives a letter addressed to Mr. H. Potter inviting him to Hogwarts School of Witchcraft and Wizardry. Sceptical, he nevertheless agrees to a visit from Deputy Headmistress Minerva McGonagall for a demonstration of magic. With magic now seemingly a proven reality, Harry now takes his place at Hogwarts, "armed with Enlightenment ideals and the experimental spirit."