Fanon is a term used to refer to "fan canon" (of which the term is a portmanteau). It applies to certain "facts" that may have been accepted as a truth by a large number of fans, and thus either replaces an established canonical fact in the minds of those fans, or fills a plot-hole.
Examples of fanon
- The First Age began with the first sunrise over Middle-earth and the events of The Lord of the Rings took place in the Third Age of the Sun.
- Actually, Tolkien never described his ages as being linked to the Sun and specifically wrote that the "First Age of the Children of Ilúvatar" began with the Awakening of the Elves, long before the first sunrise. Despite this, many fans believe the 'Ages of the Sun' version is correct because it has been repeated so often.
- Fingon and Maedhros were lovers.
- This concept, which frequently appears in slash fan fiction (where writers explore homosexual pairings), derives from their close friendship in the book, but would most likely have been rejected by Tolkien, a devout Roman Catholic. The less detailed nature of the Silmarillion narrative in comparison to The Lord of the Rings gives fan fiction writers more leeway for developing a Fingon-Maedhros romance and its possible historical significance than exists with respect to a Frodo-Sam or Aragorn-Legolas relationship.
- The friendship of Frodo and Sam had homoerotic overtones.
- This concept, which has generated a great deal of slash fan fiction, derives from a modern interpretation of a book written in a different era, and would also have been likely rejected by Tolkien. (In an amusing nod to this idea, when TBS aired the film trilogy, some of their ads implied a homosexual relationship between Frodo and Sam, with the song "Secret Lovers" being played during the commercial.)
- The friendship of Aragorn and Legolas had homoerotic overtones.
- As with Frodo and Sam, this idea has produced a large amount of slash and would most likely have been rejected by Tolkien. However, this case is slightly different in that the idea largely derives from the films rather than the books, since the films emphasize the Aragorn-Legolas friendship more than the books do.
- The Arkenstone was a Silmaril, probably the one thrown into a fiery pit by Maedhros, and found its way (geologically?) to the north, to be rediscovered by the Khazad of Erebor.
- Late in the life of Elros his brother Elrond visited him in Númenor and was shocked to see how old he had grown, having chosen the mortality of Men.
- An obscure note published in The Lost Road and Other Writings implies that Tolkien considered the possibility that Elrond and Elros originally sailed to Númenor together and that Elrond later returned to Middle-earth. However, there is no reference in Tolkien's writings to Elrond visiting Elros in his old age.
- Elladan and Elrohir, the twin sons of Elrond, are jokesters and tricksters.
- This is a common characterization of them in fan fiction and may have been inspired by the depiction of the Weasley twins in J.K. Rowling's Harry Potter books as well as that of Merry and Pippin in Peter Jackson's films.
- Celebrían, the mother of Arwen, wife of Elrond and daughter of Galadriel, was raped by the Orcs who captured her.
- According to this theory, Tolkien intended to convey the fact of the rape obliquely when he wrote that Celebrían received a "poisoned wound". This idea may or may not be contradicted by Tolkien's statement (in the notes to "Laws and Customs Among the Eldar" in Morgoth's Ring) that Elves passed directly to Mandos (i.e. die) if they were raped, since that statement seems to refer specifically to rape committed by an Elf.
- Aragorn may have become the biological father of Boromir and/or Faramir during his time in Gondor as "Thorongil".
- According to Appendices A and B of The Lord of the Rings, "Thorongil" departed from Gondor in T.A. 2980; Boromir was born in 2978 and Faramir in 2983. Thus Aragorn was apparently in Gondor at the time of Boromir's birth (but not Faramir's). However, there is no evidence whatsoever in Tolkien's writings for an affair between Aragorn and Finduilas (the wife of Denethor). Such an occurrence would contradict Tolkien's devout Catholic viewpoint and the fact that Aragorn was raised among the Elves, for whom adultery was unthinkable.
- Faramir was known as "the Raven of Gondor" due to his status as the guardian of Ithilien.
- This concept apparently derives from Tolkien describing Faramir's hair color as "raven". The designers of The Two Towers film used ravens as a visual motif for Faramir. However, the title "the Raven of Gondor" is never used in Tolkien's writings or in the films.
- Arwen was the last Elf born in Middle-earth.
- This concept derives from publicity for the films, but is never stated in the films or the books.
- Legolas is 2931 years old during the War of the Ring, and thus was born in T.A. 87.
- This information also comes from film publicity and is never stated in the films or books. It may derive from the fact that Aragorn was born in the year T.A. 2931. The date of T.A. 87 for Legolas' birth agrees with another common fan theory, namely that Legolas was born during the period of peace at the beginning of the Third Age. This is neither confirmed nor denied by Tolkien, who never reveals Legolas' birthdate.
- Legolas is blond.
- This is a visual tradition dating back to the works of the Brothers Hildebrandt in the 1970s and followed in both the animated and live action LotR films. However, Tolkien never specifies Legolas' hair color (although The Hobbit mentions that Thranduil, Legolas' father, was blond). Legolas' hair color is one of the most enduring controversies in Tolkien fandom.
- Thranduil, Legolas' father, was an abusive parent.
- This characterization appears frequently in fan fiction and is proposed as an explanation for Legolas being sent to Rivendell and for his referring to Thranduil as "my Elven lord" rather than "my father". However, The Hobbit depicts Thranduil in reasonably positive terms, especially given his status as the Dwarves' antagonist for part of the story.
- The names of all nine Nazgûl are known: Er-Murazor (the Witch-king of Angmar), Khamûl, Dwar of Waw, Ji Indur Dawndeath, Akhorahil, Hoarmurath, Adunaphel the Quiet (female — see below), Ren the Unclean and Uvatha the Horseman.
- In fact Tolkien recorded the name of only one Nazgûl: Khamûl, the Black Rider who barely missed catching the Hobbits at Bucklebury Ferry. Even the personal name of the Witch-King of Angmar was not given by Tolkien, although some fans refer to him as "Angmar". The names for the eight Nazgûl other than Khamûl which some fans think were coined by Tolkien were actually invented for the Middle-earth Role Playing game (MERP) published by Iron Crown Enterprises (ICE).
- One of the nine Nazgûl was female.
- This concept also comes from MERP. Tolkien's texts seemingly contradict this idea with their consistent references to the Nazgûl as "Men" and "kings", although it could be argued that "Men" includes women and "kings" includes queens. Unsurprisingly, the film version of The Fellowship of the Ring contradicts this idea by showing all nine Nazgûl as men when they received their Rings of Power.
- There is an Elven-archer in Mirkwood named Silindë, described as a tall, blond Sinda. **Silindë is Quenya and should not be used to name an Elf in Mirkwood. Nor is it likely that a Sinda would be blond. Silindë is one of the more prominent characters in a large group of Elves in the films whose names are in use on the Internet despite not being established by Tolkien. Some of these Elves (including Silindë) were named in Decipher Inc.'s The Lord of the Rings Trading Card Game; others were simply assigned names by Internet fandom. The Elf named Silindë by Decipher appears at the Council of Elrond in the film of The Fellowship of the Ring, and is played by Sam Kelly.
- The name of Legolas' mother is known.
- In fact a name was coined for her for MERP, but never by Tolkien.
- The War of the Ring included a "War in the North", which involved fighting in Eriador and around Rivendell.
- This has been stated as fact by the writers of the films in a DVD commentary and has formed the basis for parts of the 2006 computer game The Lord of the Rings: The Battle for Middle-earth II. However, although Tolkien mentions violent incidents around Bree during the War (not to mention the Scouring of the Shire), no extensive military campaign in Eriador is mentioned in the Tale of Years in Appendix B of The Lord of the Rings. Since the Tale of Years does mention the Battle of Dale and the fighting around Lothlórien, it is clear that it would also have mentioned the "War in the North" if it had been part of Tolkien's conception. Moreover, the section of Appendix A on the Dwarves includes comments by Gandalf to the effect that extensive, destructive fighting in Eriador was averted by the death of Smaug and the Battles of Five Armies and of Dale.
- In addition to their son Eldarion, Aragorn and Arwen had as many as four or eight daughters.
- The whole continent of Middle-earth resembles Europe with respective continents for Asia and Africa, while Valinor is in the place of the United States and has a crescent shape.
- This derives from The Atlas of Middle-earth, which tried to composite a map of Arda based on a drawing by Tolkien (made in the late 1930s or early 40s and published in The Shaping of Middle-earth) and the later well-known maps of Beleriand and the coasts of Middle-earth. Although this old map generally fits the descriptions of the canonical Silmarillion, it is a matter of debate whether earlier concepts of Tolkien's can be used to fill the gaps of later works such as LotR.
- Elves and Hobbits have pointy ears.
- Hobbits have huge feet.
- Tolkien wrote: "their feet had tough leathery soles and were clad in a thick curling hair, much like the hair of their heads". The idea that they have very large feet, as depicted in the movies, probably derives from illustrations by the Brothers Hildebrandt.
- Déagol is Sméagol's cousin.
- Tolkien only calls him Sméagol's friend in The Lord of the Rings, though in The Letters of J. R. R. Tolkien he writes that Déagol was "evidently a relative (as no doubt all the members of the small community were)" of Sméagol’s. This fanon probably dates from The Complete Guide to Middle-earth by Robert Foster and Tolkien: The Illustrated Encyclopedia by David Day. 
Other kinds of fanon
Due to the nature of the work, much pseudo-scientific speculation is encouraged in order to explain motivations, facts, reactions and generally fill some gaps. This differs from proper fanon since such study does not invent new elements from scratch, but rather attempts to reveal how canon is. See also Tolkienology.
Fanon can also take the form of personal beliefs held by individuals. In this case, an individual may create an expansive backstory, possibly a fan fiction, which they accept as "true." These have less standing than even the fanon mentioned above, and thus are not included on Tolkien Gateway.