Keith Giffen was born in Queens, New York City. Giffen is known for having an unconventional writing style, often taking a new approach when writing a character, and sometimes ignoring past continuity.

He is possibly best-known for his long runs illustrating, and later writing the Legion of Super-Heroes in the 80's and 90's. He also created the mercenary, Lobo and the zany Ambush Bug. He has worked on several titles over the years, including All-Star Comics, Doctor Fate, Drax the Destroyer, Heckler, Nick Fury's Howling Commandos, The Defenders, Suicide Squad, Justice League International, Trencher, T.H.U.N.D.E.R. Agents, Magnus Robot Fighter. For a while, he took a break from comics and worked in the television and film industry, including shows as The Real Ghostbusters and Ed, Edd 'n' Eddy.

Keith Giffen was the breakdown artist on 52 and Countdown to Final Crisis. He was also the lead writer for Marvel's Annihilation event. He currently writes Doom Patrol and Booster Gold for DC, and it has been reported that he will be working on the Legion of Super-Heroes Annual.

Giffen's art has taken on many styles over the years. His early work tended towards a heavy influence from Jack Kirby. When he returned to comics after a hiatus, his style was more precise and reminiscent of George Perez and Jim Starlin, and helped make the Legion of Super-Heroes DC's second most popular comic. It was his work on the Legion that rocketed him to comic book fame and gave him a creative control with the national companies that few artists achieved. He peppered his artwork with in-jokes such as upside down Superman logos, hidden Marvel characters, eyeball creatures, and scrawled humorous messages on signs in the background of his panels in the alternate futuristic alphabet known as Interlac.

Soon thereafter he developed a scratchier, more impressionistic style, using a highly stylized method of drawing directly with ink, on titles such as Trencher, Lobo: Infanticide and Images of Shadowhawk. After his lengthy sabbatical from comics work, Giffen returned with a style that some said was influenced by his Justice League artist Kevin Maguire that was mid-way between the tight, controlled pencils of his early Legion days and the freer but less anatomically correct style he had later adopted.

For many years, Giffen would co-write comics, but only as a plotter. He relied on others such as Robert Loren Fleming, and Tom and Mary Bierbaum to supply dialogue, even when he was basically the author of the work. Beginning with Trencher, Giffen started writing comics fully by himself, although he still collaborates when the project calls for it.

Giffen is known for having an unorthodox writing style, often using characters in ways not seen before. His dialogue is usually characterized by a biting wit that is seen as much less zany than dialogue provided by longtime collaborators DeMatteis and Fleming. That approach has brought him both criticism and admiration,as perhaps best illustrated by the mixed (although commercially successful) response to his work in Justice League International.

He is also known for his humorous takes on existing characters, often focusing on their personality clashes. He also has a tendency to poke fun at trends in comic books or character archetypes. His Ambush Bug miniseries is especially noted for its in-jokes such as Villian the Villain, Cheeks the Toy Wonder, and the use of DC editor Julius Schwartz as a character.

Giffen was also added to the writing team for the weekly The New 52: Futures End weekly series alongside other writers such as Brian Azzarello, Jeff Lemire, and Dan Jurgens

Some Characters Created by Keith Giffen

• Ambush Bug
• Aagog
• Aaban Tariq
• Aegis
• Annihilation Wave
• Ariel Masters
• Arsenal
• Azur Te
• Banger
• Beefeater
• Big Sir
• Bleeding Adonis
• Blood Rose
• Blue Beetle(Reyes)
• Botfly
• Cammi
• Carny
• Catherine Cobert
• Cheeks
• Coeval
• Coil
• Colonel Rumaan Harjavti
• The Convert
• Dr. Diehard
• Dreamslayer
• Elton Kookaburra
• Enchanthrax
• Errata
• Ethan Boyer
• Fallen One
• Fifty Sue
• Firestorm (Payne)
• G'Nort
• Gorgon
• Gray Man
• Ice
• Ilda
• Jack of Hearts
• Jacques Foccart
• Jediah Caul
• Jody Robbins
• Justin
• Kali
• Kevin Kho
• L-Ron
• Laord of the Hunt
• Lobo
• Locus
• Lord Havok
• Manga Khan
• Martin Welman
• Mash
• Maxwell Lord
• Mercy
• Midas
• The Mighty Bruce
• Porcelain Doll
• Queen Bee
• Rocket Raccoon
• Rocket Red
• Stormguard
• Silver Sorceress
• Sky Witness
• Sweet Leilani
• Tenebrous
• Teri
• Terry
• Thumpa
• Tracer
• Vext
• Warwolf
• The Wanderer
• Wandjina
• Woodgod
• Xum of All Things