Mike W. Barr is an American writer of comic books, and mystery, and science fiction novels. Barr's debut as a comics professional came in DC Comics' Detective Comics #444 (Dec. 1974-Jan. 1975), for which he wrote an 8-page back-up mystery feature starring the Elongated Man. Another Elongated Man story followed in Detective Comics #453 (November 1975). He wrote text articles and editorial replies in letter columns for the next few years. By mid-1980 he was writing regularly for both DC and Marvel, including stories for Marvel Team-Up, Mystery in Space, Green Lantern, and various Batman titles.

Legion of Super-Heroes #277 (July 1981) saw him take on editorial duties at DC, while writing issues of DC's Star Trek comic, for whom he created the native American character Ensign Bearclaw and a pacifist Klingon named Konom. In December 1982, he and artist Brian Bolland began Camelot 3000, a 12 issue limited series that was one of DC Comics' first direct market projects. In August 1983, Barr created what may well be his most enduring work, the monthly title Batman and the Outsiders with art by Jim Aparo. Barr wrote every issue of the original series, and its Baxter paper spinoff, The Outsiders.

His other comics work includes Mantra and Maze Agency as well as the 1987 OGN hardcover book Batman: Son of the Demon (with art by Jerry Bingham), proceeds from which reputedly "restored DC Comics to first place in sales after fifteen years." This title, and Barr's work on Batman with artist Alan Davis have been cited by Grant Morrison as key inspirations for his recent (2006) run on the Batman title.

In 2007, he wrote a two-part story for the pages of DC's JLA: Classified (#47-48, Jan-Feb 2008), returned to the Outsiders with Outsiders: Five of a Kind—Katana/Shazam #1 (Oct 2007), contributed to Tokyopop's Star Trek: The Manga, and relaunched Maze Agency at IDW Publishing. He has also scripted many of Bongo Comics' Simpsons titles, including a Christmas story for 2010.

In May 2010, the Invisible College Press published Barr's science fiction/fantasy novel, Majician/51, about the discoveries of a scientist working at Area 51.