Katana (Tatsu Yamashiro (山城 タツ, Yamashiro Tatsu)) is a superheroine appearing in American comic books published by DC Comics. First appearing in 1983, Katana is a samurai warrior whose skill with a sword allows her to fight for justice as a superheroine. Her tragic backstory includes the death of her husband, Maseo, whose soul becomes trapped in her blade, the Soultaker.

Katana has been part of various DC Comics superhero teams, including the Justice League and Birds of Prey, but is most commonly associated with the Outsiders, a team of heroes hand-picked by Batman to act as his personal black ops team, handling riskier missions. Of the character's first appearances, one critic has noted, "The idea that a superhero would wield a sword which caught the souls of the wielder’s victims was not very superhero-y. But Katana was from the start a rough and tumble character happy to use throwing stars as weapons (even if she usually used the flat of her sword otherwise)."

In the 2010s, DC began to feature the character much more extensively in media adaptations of its comic books, including a recurring role in the animated series Batman: The Brave and the Bold and a starring role in the series Beware the Batman. The character was portrayed by Rila Fukushima in the Arrowverse TV series Arrow and by Karen Fukuhara in the 2016 DC Extended Universe film Suicide Squad. Katana has also been featured in direct-to-video animated films and a number of DC Comics video games.

In a 2015 interview with ComicsAlliance, Mike W. Barr spoke on the character's genesis, stating:

When we created Batman and the Outsiders, we brought in, of course, Black Lightning and Metamorpho, who were pre-existing characters, which we thought would give the series some sort of gravitas and a sense of existing in the DC Universe. Then we needed three new characters, and so far, none of the characters we'd picked for the Outsiders had been women, so I decided that there would be an almost mini-Batman-and-Robin team, Katana and Halo. I'd always been interested in Japanese culture and samurai, so I decided that the character of Katana would be a female samurai.

Katana first appeared in The Brave and the Bold #200 (cover-dated July 1983) and was created by writer Mike W. Barr and artist Jim Aparo. She is frequently a member of "team" publications such as Batman and the Outsiders, Birds of Prey (during the New 52 era), and Suicide Squad (during the DC Rebirth era).

In February 2013, Katana received her own series as part of The New 52, written by Ann Nocenti and with art by Alex Sanchez. Katana lasted for ten issues, with the final issue being released on December 11, 2013.

Tatsu Yamashiro (山城 たつ) is an average Japanese girl, save for her proficiency in the martial arts, a trait encouraged by her parents. Two brothers—Maseo and Takeo Yamashiro (from whom she gained her current surname)—both proclaim their love for her. While she likes both, she chooses Maseo as her husband. Enraged, Takeo refuses to attend the couple's wedding. Maseo disowns his brother, who joined the yakuza and took their mark of a dragon tattoo across his chest. Tatsu and Maseo, mourning the deaths of Tatsu's parents, start a family of their own. Tatsu gives birth to twins, Yuki and Reiko. Meanwhile, Takeo rises through the yakuza ranks and indulges his "exotic tastes" for ancient weapons. He is presented with twin swords by General Karnz (later henchman to Baron Bedlam), one of which Takeo favors for its mystical properties.