Keith Robert Andreassi DeCandido (born April 18, 1969) is an American science fiction and fantasy writer and musician, who works on comic books, novels, role-playing games and video games, including numerous media tie-in books for properties such as Star Trek, Buffy the Vampire Slayer, Doctor Who, Supernatural, Andromeda, Farscape, Leverage, Spider-Man, X-Men, Sleepy Hollow, and Stargate SG-1.

Along with John S. Drew, in the 1990s he co-produced a public-access television cable TV show in Manhattan about science fiction called The Chronic Rift, which he also co-hosted.

While DeCandido spent much of his career writing Star Trek fiction, he has written tie-ins for other popular sci-fi and fantasy series as well, such as Buffy the Vampire Slayer, Doctor Who, Supernatural, Stargate SG-1, Sleepy Hollow, Farscape, and Leverage as well as comic books (Spider-Man, X-Men), movies (Cars, Serenity, Alien), role-playing games (Dungeons & Dragons), and video games (World of Warcraft, StarCraft, Command & Conquer, Resident Evil).

He has also written fiction in universes of his own creation: Dragon Precinct and its sequels, a high-fantasy police procedural; urban fantasy short stories set in Key West about a weirdness magnet named Cassie Zukav, who learns she is a Dís; the Adventures of Bram Gold, urban fantasy novels set in the Bronx; Super City Cops, novels, novellas, and short stories featuring cops in a city filled with superheroes; and Supernatural Crimes Unit, an urban fantasy series debuting in 2025 from the Weird Tales Presents imprint of Blackstone Publishing.

He has contributed in the past to both the Replacement Level Yankees Weblog and Pinstripe Alley, and he currently serves as an occasional freelance editor for the Society for American Baseball Research.