Peter Milligan (born 24 June 1961) is a British comic book writer who has written extensively for both British and American comic book industries. In the UK, Milligan has contributed to numerous anthology titles including 2000 AD, Revolver, Eagle and A1, and helped launch the magazine Deadline. In the US, he is best known for his frequent contributions to DC Comics' Vertigo imprint, which include the revamped DC properties Shade, the Changing Man and Human Target, a four-year run on the imprint's premier title Hellblazer, and original series Enigma, The Extremist, Egypt and Greek Street, as well as the Marvel series X-Statix, co-created by Milligan and artist Mike Allred.

Milligan started his comic career with Sounds music paper's comic strip The Electric Hoax, with Brendan McCarthy, with whom he went to art school. Milligan later moved to write short stories for 2000 AD in the early 1980s. By 1986, Milligan had his first ongoing strip in 2000AD called "Bad Company", with artists Brett Ewins and Jim McCarthy. "Bad Company" was a popular future war story and helped Milligan become better known.

Concurrently, Milligan, Ewins and Brendan McCarthy had been working on the anthology title, Strange Days for Eclipse Comics. Strange Days featured three strips, "Paradax", "Freakwave", and "Johnny Nemo". Milligan, McCarthy and Ewins produced three issues of this psychedelic comic, it was not a great seller but it picked up a small, loyal readership. The most conventional strip, "Johnny Nemo", had its own series, while the more quirky "Paradax" had a two-issue series published by Vortex Comics in 1987.

By 1989, Milligan was swapping between strips such as "Bad Company", while still writing material in 2000AD, such as "Hewligan's Haircut" with artist Jamie Hewlett. Milligan and artist Jim McCarthy created the Steve Ditko-inspired "Bix Barton". This was first run as a black and white strip for its first outing, "Barton's Beasts"; the second strip was called "Carry On Barton" (originally "Carry On Snuffing"). The strip was very popular and was a precursor of "Devlin Waugh" and others.

In 1989, he had his first work published by DC Comics. Skreemer was a six-issue mini-series (May 1989 – October 1989) drawn by Brett Ewins that was somewhat lost in the midst of the so-called "British Invasion" of American comics of the time. A dark post-apocalyptic gangster story, the series received critical acclaim, but did not sell well. Milligan was soon to become a regular writer for DC while still working on his more personal comics in the United Kingdom in comics such as 2000 AD, and its spin-off titles Crisis and Revolver.

The 1990s saw Milligan revamp Steve Ditko's character Shade, the Changing Man for DC Comics. This proved his most successful American comic, and came at the end of the first wave of the "British Invasion". With issue No. 33 (March 1993), it became part of the Vertigo imprint. It was cancelled with issue No. 70 (April 1996). A one-off story marking Vertigo's tenth anniversary was published in 2003.

Milligan succeeded Grant Morrison on Animal Man for a six-issue run in 1990–1991, and became the regular writer of Batman in Detective Comics in the same year. During an editorial meeting, Milligan presented the idea that led to the creation of Azrael, who became Batman during the "Knightfall" crossover.

Skin (art by Brendan McCarthy) was the story of a young thalidomide skinhead in 1970s London, and his attempts to deal with his disability and the world in general. The strip was due to feature in Crisis in 1990 but the publishers Fleetway were worried by the controversial subject matter, plus they were concerned with the use of explicit language in the story. The printers refused to print it, blaming the graphic language and controversial subject matter as a reason. The story remained in limbo until eventually being published as a graphic novel by Tundra Press to little controversy.