In the writings of J.R.R. Tolkien, the "Fall of Gondolin" is the name of one of the original Lost Tales which formed the basis for a section in his later work, The Silmarillion.

"The Fall of Gondolin" tells of the founding of the Elven city of Gondolin (built in secret by Turgon and his people), of the arrival Tuor, a prince of the Edain, of the betrayal of the city to Morgoth by Turgon's nephew Maeglin, and of its subsequent destruction by Morgoth's armies.

J.R.R. Tolkien actually began writing the story that would become "The Fall of Gondolin" in 1917 in an army barracks on the back of a sheet of military marching music. It is more or less the first traceable story he wrote down on paper about the Middle-earth legendarium.

Because Tolkien was constantly revising his First Age stories, the narrative he wrote in 1917 (published postumously in the Book of Lost Tales) remains the only full account of the fall of the city. The narrative in The Silmarillion was the result of the editing by his son Christopher of various different sources.

A partial new version of "The Fall of Gondolin" was published in the Unfinished Tales under the title "Of Tuor and his Coming to Gondolin". Actually titled "Of Tuor and the Fall of Gondolin", this narrative shows a great expansion of the earlier tale. It can be surmised from this text that Tolkien would have rewritten the entire story, but for reasons that are not known he abandoned the text before Tuor actually arrives in the city. For this reason Christopher Tolkien retitled the story before including it in Unfinished Tales.