What is the name of the first story in Tolkien’s earliest Middle-earth collection, The Book of Lost Tales?

The first story in Tolkien’s The Book of Lost Tales is The Cottage of Lost Play.

The Book of Lost Tales was Tolkien’s earliest prose version of the mythology that later developed into the history of Middle-earth. He began writing these stories during and after World War I, and they were later edited and published by Christopher Tolkien in two volumes of The History of Middle-earth.

The Cottage of Lost Play introduces Eriol, a human visitor who reaches a mysterious house in the Elvish settlement of Kortirion. There he hears the Lost Tales, which provide a frame for stories about the early history of the Elves and the world.

Many names, plots, and concepts in this early collection changed substantially in Tolkien’s later writings. The Fall of Gondolin and The Tale of Tinúviel are also important early tales, but they are separate stories within the collection rather than its opening tale.