Girl Genius is an ongoing comic book series turned webcomic, written and drawn by Phil and Kaja Foglio and published by their company, Studio Foglio LLC under the imprint Airship Entertainment. The comic has won five WCCA awards including 2008 Outstanding Comic, and been nominated for a Hugo Award for Best Professional Artist, an Eagle Award and twice for an Eisner Award; in 2009, 2010, and 2011 it won the Hugo Award for Best Graphic Story.

Girl Genius has the tagline of "Adventure, Romance, MAD SCIENCE!". It features a female lead character in an alternate-history Victorian-style "steampunk" setting, although elements veer from what is usually thought of as steampunk. Kaja Foglio, one of the co-creators, describes it as "gaslamp fantasy" instead to suggest its more fantastic style.

The Foglios have also released a novel titled Agatha H. and the Airship City.

The specific idea for the style of Girl Genius came about when Kaja Foglio went through some of Phil's loose drawings: "I was going through all of Phil's old files and I was filing all of the old sketches, and I was coming across weird airships and cats in tophats with walking canes, and all of this... wonderful... Victoriana sci-fi stuff... it was like 'Oh, this is everything I love!'" CBR News quoted Phil Foglio as saying, "We wanted to do something with a strong female lead character. We both like the tropes associated with mad science, and I really enjoy drawing fiddley Victorian style gizmos". After some intensive long-term plotting starting in 1993, the Foglios announced the publication of Girl Genius in 2000.