Del Rey often told people that his real name was Ramon Felipe Alvarez-del Rey (or sometimes even Ramon Felipe San Juan Mario Silvio Enrico Smith Heartcourt-Brace Sierra y Alvarez del Rey y de los Uerdes). He also claimed that his family was killed in a car accident during 1935. However, his sister has confirmed that his name was really Leonard Knapp and that while the accident in 1935 killed his first wife, his parents, brother, and sister were not killed in the accident.

Del Rey first started publishing stories in pulp magazines during the late 1930s, during the beginning of the so-called Golden Age of Science Fiction. He was associated with the most prestigious science fiction magazine of the era, Astounding Science Fiction, and its editor, John W. Campbell, Jr. During the 1950s, del Rey was one of the main science fiction writers writing for adolescents (along with Robert A. Heinlein and Andre Norton). During this time some of his fiction was published by the name "Erik van Lhin".

During a period when del Rey's work wasn't selling well, he worked as a short order cook at the White Tower Restaurant in New York. After he married his second wife, Helen Schlaz, during 1945, he quit that job to write full time. After meeting Scott Meredith at the 1947 World Science Fiction Convention, he began working as a reader for Scott Meredith's literary agency, where he also served as office manager.

He later became an editor for several pulp magazines and then for book publishers. During 1952 and 1953, del Rey edited several magazines: Space SF, Fantasy Fiction, Science Fiction Adventures (as Philip St. John), Rocket Stories (as Wade Kaempfert), and Fantasy Fiction (as Cameron Hall). He was most successful editing for Ballantine Books with his final wife, Judy-Lynn del Rey, and initiated a science fiction division with her at Ballantine, Del Rey Books, during 1977.

During 1957, del Rey and Damon Knight co-edited a small amateur magazine named Science Fiction Forum. In response to a debate about symbolism within the magazine, del Rey accepted Knight's challenge to write an analysis of James Blish's story "Common Time" that showed the story was about a man eating a ham sandwich.

After science fiction gained respectability and began to be taught in classrooms, del Rey stated that academics interested in the genre should "get out of my Ghetto." Del Rey stated that "to develop science fiction had to remove itself from the usual critics who viewed it from the perspective of [the] mainstream, and who judged its worth largely on its mainstream values. As part of that mainstream, it would never have had the freedom to make the choices it did — many of them quite possibly wrong, but necessary for its development."

Del Rey was a member of an all-male literary banqueting club the Trap Door Spiders, which served as the basis of Isaac Asimov's fictional group of mystery solvers the Black Widowers. Del Rey himself was the model for the "Emmanuel Rubin" character.

Awards

Del Rey was awarded the 1972 E. E. Smith Memorial Award for Imaginative Fiction (the Skylark Award) by the New England Science Fiction Association for "contributing significantly to science fiction, both through work in the field and by exemplifying the personal qualities that made the late "Doc" Smith well-loved by those who knew him". He was awarded the 1985 Balrog Special Award (organized by Locus Magazine), a fan-voted award for works of fantasy. He was also awarded the 1990 Grand Master Award by the Science Fiction and Fantasy Writers of America for lifetime achievement in science fiction and/or fantasy.

Fiction

Novels

• Marooned on Mars (1952)
• Rocket Jockey as Philip St. John (1952)
• Attack from Atlantis (1953)
• Battle on Mercury as Erik Van Lhin (1953)
• The Mysterious Planet as Kenneth Wright (1953)
• Rockets to Nowhere as Philip St. John (1954)
• Step to the Stars (1954)
• Preferred Risk (1955) with Frederik Pohl [as by Edson McCann]
• Magazine/Anthology Appearances:
• Preferred Risk (Part 1 of 4) (1955) with Frederik Pohl
• Preferred Risk (Part 2 of 4) (1955) with Frederik Pohl
• Preferred Risk (Part 3 of 4) (1955) with Frederik Pohl
• Preferred Risk (Part 4 of 4) (1955) with Frederik Pohl
• Mission to the Moon (1956)
• Nerves (1956)
• Police Your Planet as Erik Van Lhin (1956)
• Day of the Giants (1959)
• Moon of Mutiny (1961)
• The Eleventh Commandment (1962)
• Outpost of Jupiter (1963)
• The Runaway Robot (1965) was published with del Rey's byline, but was actually ghost-written by Paul W. Fairman based on an outline by del Rey. Lester del Rey
• The Infinite Worlds of Maybe (1966)
• Rocket from Infinity (1966)
• The Scheme of Things (1966)
• Siege Perilous (1966)
• Tunnel Through Time (1966)
• Prisoners of Space (1968)
• Pstalemate (1971)
• The Sky Is Falling (1973)
• Badge of Infamy (1973)
• Weeping May Tarry (1978) with Raymond F. Jones

Collections

• ...And Some Were Human (1948)
• Robots and Changelings (1957)
• The Sky is Falling and Badge of Infamy (1966)
• Mortals and Monsters (1965)
• Gods and Golems (1973)
• The Early del Rey (1975)
• The Early del Rey: Vol 1 (1976)
• The Early del Rey: Vol 2 (1976)
• The Best of Lester del Rey (1978)
• War and Space (2009)
• Robots and Magic (2010)

Nonfiction

• Rockets Through Space (1957)
• Space Flight, Golden Press, 1959
• The Mysterious Earth (1960)
• The Mysterious Sea (1961)
• The Mysterious Sky (1964)
• The World of Science Fiction, 1926-1976: the History of a Subculture (1980)

Edited

• The Year After Tomorrow with Carl Carmer & Cecile Matschat (1954)
• Best Science Fiction of the Year #1-#5 (1972-1976)