The Hobbit was J.R.R. Tolkien’s first published Middle-earth story, written as a children’s book.
Tolkien began The Hobbit during the 1930s, developing a tale about Bilbo Baggins, a comfort-loving Hobbit drawn into an adventure involving dwarves, a lost kingdom, and a dragon. It was published in 1937 and quickly became successful.
Although the book has a lighter tone than The Lord of the Rings, it contains characters and objects that became central to Tolkien’s larger legendarium. The discovery of the One Ring is the most important example.
Tolkien’s earlier private writings about Middle-earth existed in manuscript form, including versions later connected with The Book of Lost Tales. Those unpublished texts are why “first published story” is more precise than simply calling The Hobbit his first Middle-earth writing.