What was the name of J.R.R. Tolkien’s first published Middle-earth story after The Hobbit?

The Lord of the Rings was J.R.R. Tolkien’s first published Middle-earth story after The Hobbit.

Tolkien began writing it as a sequel to The Hobbit, but the project expanded into a much larger work involving the history of the One Ring, the fall of Sauron, and the fate of Middle-earth. It was published in three volumes from 1954 to 1955, seventeen years after The Hobbit.

The Silmarillion was published only after Tolkien’s death, in 1977, and is mainly a collection of mythological and historical material edited by Christopher Tolkien. Unfinished Tales was also posthumous. Those books are important to Tolkien’s legendarium, but neither was his next published Middle-earth narrative after The Hobbit.