What fictional book contains the history of the One Ring in J.R.R. Tolkien’s The Lord of the Rings?

The fictional book containing the history of the One Ring in J.R.R. Tolkien’s The Lord of the Rings is the Red Book of Westmarch.

The Red Book of Westmarch is presented as the source behind Tolkien’s narrative. Bilbo Baggins begins its account by recording his adventures, including the discovery of the One Ring. Frodo adds his own account of the quest to destroy it, and Samwise Gamgee completes and preserves the record.

The book is said to have been kept in the Westmarch, a region of the Shire. Tolkien’s framing device makes the events feel like a translated historical record rather than an authorless modern narrative. It also explains why Bilbo’s memoir, There and Back Again, and Frodo’s account appear within the larger history.

The Book of Mazarbul is a different object: a record found in the mines of Moria. The Red Book should also not be confused with Tolkien’s real-world manuscripts or with The Silmarillion, which covers much earlier mythology.