Blue Gender is a Japanese anime television series created by Ryōsuke Takahashi, the creator of Armored Trooper Votoms and Gasaraki, broadcast in Japan from 1999 to 2000 and spanning 26 episodes. Blue Gender was animated by the Japanese studio AIC and distributed in the United States by Funimation - one of the company's first non-Dragon Ball licenses. In 2003, Blue Gender was released on American television as part of Cartoon Network's Adult Swim block, though it had originally been planned for a Toonami broadcast, and was thus edited to remove more of its graphic violence, nudity, and sex scenes than usual, even for Adult Swim's standards. However, it aired uncut on the Funimation Channel in the United States.

Blue Gender is set in the 2030s, in which Earth has been overrun by the Blue-alien insectoid creatures containing a newly evolved B-cell, that kill and harvest humans for food. Most of the surviving human race has moved to Second Earth, a huge space station that orbits the planet. The series focuses on the relationship between Yuji—a human who also possesses the B-cells, and Marlene—a soldier from Second Earth, as they work together to return to Second Earth and subsequently participate in military operations against the Blue.

The series was followed by Blue Gender: The Warrior, a compilation movie with an alternative ending, in 2002. Blue Gender was also broadcast in the United Kingdom from 2002 to 2003 on the Sci Fi Channel.