Christopher Tolkien, the son of the writer J.R.R. Tolkien, who guarded his legacy and brought forth monumental posthumous works, like “The Silmarillion,” based on his father’s writings, died on Thursday in Provence, France. He was 95.

His death was confirmed by Daniel Klass, his brother-in-law.

For nearly 50 years after his father died in 1973, Mr. Tolkien worked to keep alive the world he had created in “The Hobbit” (1937) and “The Lord of the Rings” (1949) — the spiders of Mirkwood, the Eye of Mordor, the elves of Rivendell and thousands of pages’ worth of other characters, places and plot twists. In all, he edited or oversaw the publication of two dozen editions of his father’s works, many of which became international best sellers.

Mr. Tolkien was his father’s literary executor but played a far more expansive role than that title usually implies. While the elder Tolkien was writing “The Lord of the Rings,” he was also creating a vast world of legends and mythologies that he hoped would accompany the book. But he was a notorious perfectionist and was never able to put this work in publishable form before he died.

His son spent four years organizing and compiling those myths and legends, publishing them in 1977 as “The Silmarillion.”