Joseph Michael Straczynski (; born July 17, 1954) is an American television and film screenwriter, producer and director, and comic book writer. He is the founder of Studio JMS, and is best known as the creator of the science fiction television series Babylon 5 (1993–1998) and its spinoff Crusade (1999), as well as the series Jeremiah (2002–2004), and Sense8 (2015–2018).

Straczynski wrote the psychological drama film Changeling (2008) and was co-writer on the martial arts thriller Ninja Assassin (2009), horror film Underworld: Awakening (2012), and apocalyptic horror film World War Z (2013).

From 2001 to 2007, Straczynski wrote Marvel Comics' The Amazing Spider-Man, followed by runs on Thor and Fantastic Four. He is also the author of the Superman: Earth One trilogy of graphic novels, and has written Superman, Wonder Woman, and Before Watchmen for DC Comics. Straczynski is the creator and writer of several original comic book series such as Rising Stars, Midnight Nation, Dream Police, and Ten Grand through Joe's Comics.

A prolific writer across a variety of media and former journalist, Straczynski is the author of the novels Blood Night (1988), Othersyde (1990), and Tribulations (2000), the short fiction collection Straczynski Unplugged (2004), and the nonfiction book The Complete Book of Scriptwriting (1982).

Straczynski is a long-time participant in Usenet and other early computer networks, interacting with fans through various online forums (including GEnie, CompuServe, and America Online) since 1984. He is credited as being the first TV producer to directly engage with fans on the Internet, and allow their viewpoints to influence the look and feel of his show. (See Babylon 5's use of the Internet.) Two prominent areas where he had a presence were GEnie and the newsgroup rec.arts.sf.tv.babylon5.moderated.