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- Daryl F. Mallett (born 1969), USA, editor at Borgo Press (1989–1999); editor of SFRA Review #203-211 (1993–1994); editorial board of Extrapolation (1994-????); managing editor at Chaos! Comics (1995); associate editor of Other Worlds (1995-????)
- Barry N. Malzberg (born 1939), USA, magazine editor, anthologist
- Nick Mamatas (born 1972), editor of Clarkesworld Magazine; editor of Haikasoru imprint of Japanese SF in translation
- Leo Margulies (1900–1975), USA, anthologist, editor of Thrilling Wonder Stories, Captain Future, Startling Stories, and many other pulp magazines
- Shawna McCarthy (born 1954), USA, anthologist, editor of Realms of Fantasy; editor of Isaac Asimov's Science Fiction Magazine (1983–86)
- J. Francis McComas (1910–1978), USA, co-founding editor of The Magazine of Fantasy & Science Fiction; anthologist
- Harriet McDougal, USA, former Editor-in-Chief of Tor Books, former Editorial Director of Ace Books; wife of author Robert Jordan.
- Beth Meacham (born 1951), USA, senior editor at Tor Books, 1984–present; editor at Ace Books 1981–1984
- Judith Merril (1923–1997), Canada (born USA), edited "Year's Best" anthologies, (1956–67)
- Sam Merwin, Jr. (1910–1996), USA, editor of Fantastic Universe and Galaxy
- Robert P. Mills (1920–1986), USA, magazine editor
- Samuel Mines (1909–1986), USA, editor of Startling Stories and Thrilling Wonder Stories in the 1950s
- Jim Minz, USA, editor at Baen Books, former editor at Tor Books and Del Rey Books
- Betsy Mitchell, USA, editor-in-chief of Del Rey Books; former editor at Baen Books and Warner Aspect
- Michael Moorcock (born 1939), UK (lives in USA), editor of New Worlds magazine in the 1960s
- James Morrow (born 1947), USA, anthologist, editor of The SFWA European Hall of Fame
Read more about this topic: List Of Science Fiction Editors