Bilbo Baggins is 111 years old at the start of J.R.R. Tolkien’s The Lord of the Rings.
Bilbo celebrates his eleventy-first birthday at the beginning of The Fellowship of the Ring. The birthday party is held in Hobbiton, where Bilbo gives a famous farewell speech before using the One Ring to disappear and leaving the Shire.
The number is significant because Hobbits commonly live longer than Men, and Bilbo’s unusually vigorous old age is connected to his possession of the Ring. He found it during his earlier adventure, described in The Hobbit, after a meeting with Gollum beneath the Misty Mountains.
Bilbo is not the same age as Frodo. Frodo is 33 when he comes of age at the opening birthday celebration, although the main quest begins later, after Bilbo has left and the Ring’s danger has become clear. Tolkien’s use of “eleventy-first” means 111, not 110 or 101.