Bilbo Baggins is 111 years old when he holds his eleventy-first birthday party.
In The Fellowship of the Ring, Tolkien describes Bilbo’s birthday as his “eleventy-first,” meaning 111th, birthday. The celebration takes place in Hobbiton and is also Bilbo’s farewell party before he leaves the Shire. His unusual longevity is linked to his possession of the One Ring, which he obtained during the events of The Hobbit.
Bilbo’s party is a major opening scene in The Lord of the Rings. He gives a speech, disappears using the Ring, and leaves the Ring behind for Frodo. Gandalf becomes suspicious of the Ring’s nature and later investigates its history.
The number 111 is sometimes confused with Frodo’s age at the party. Frodo is 33, the traditional coming-of-age age for hobbits, and the difference between their ages is 78 years. “Eleventy-first” is Tolkien’s playful Hobbit expression for 111, not a separate fictional number.