Bilbo Baggins is the protagonist and titular character of The Hobbit and a supporting character in The Lord of the Rings, two of the most well-known of J. R. R. Tolkien's fantasy writings.
In Tolkien's narrative conceit, in which all the writings of Middle-earth are translations from the fictitious volume of The Red Book of Westmarch, Bilbo is the author of The Hobbit and translator of various "works from the elvish", as mentioned in the end of The Return of the King.
Read more about Bilbo Baggins: Portrayals in Adaptations, Family Tree