Cassandra Cain is a superheroine appearing in American comic books published by DC Comics. Created by Kelley Puckett and Damion Scott, Cassandra Cain first appeared in Batman #567 (July 1999). Commonly associated with the superhero Batman, Cassandra is one of the several characters who has assumed the role of Batgirl. Over the years, she has also assumed the names of Black Bat and Orphan. Originally the first character to star in an ongoing Batgirl comic book series, she is later replaced by Stephanie Brown in 2009. Later absent following the New 52 reboot, she later was brought back in Batman & Robin Eternal (using the code name Orphan) with a new background until her full history was restored in 2021 following the Infinite Frontier relaunch.

Her origin story presents her as the daughter of world-class assassins, David Cain and Lady Shiva, abused and raised by the former in an unusual conditioning by depriving her of speech and human contact during her childhood, supplementing combative arts and violence as her first form of communication in an effort to create a world-class fighter, assassin, and successor. While initially mute and illiterate as a result, she was an exceptional martial artist with an uncanny ability of interpreting body language efficiently. Following an encounter with Barbara Gordon and Batman, both would eventually teach her lost skills when the latter takes her under his tutelage due to her abilities and bravery and becomes a superhero within the Batman Family, and one of the world's most capable martial artists, and among Batman's adoptive children. Primarily affiliated with the Batman family, the character has also been a member other superhero teams such as the Outsiders and Birds of Prey.

Since her debut, she is considered one of the most compelling characters in Batman's fictional universe. A fan-favorite character, Cassandra is often viewed as a positive in Asian representation within superhero comics. The character would make her cinematic debut in the DC Extended Universe film Birds of Prey, portrayed by Ella Jay Basco. She would also make several animated appearances such as in Young Justice and Batwheels, the former renaming her Cassandra Wu-San.

Cassandra Cain first appeared in Batman #567 (July 1999), written by Kelley Puckett and penciled by Damion Scott (who are generally credited with her invention).

In 2000, Cassandra became the first Batgirl to be featured in an eponymous ongoing comic book series. ^{[citation needed]}

During the "War Games" story arc in 2004, Batman relies heavily on Cassandra to help control the violence of the gang war in Gotham City.^[specify]

Cassandra took on the role of a villain by becoming the head of the League of Assassins following the "One Year Later" continuity jump, as established in Robin #150 (July 2006). ^{[citation needed]}

Cassandra then appears in Supergirl (vol. 5) #14 (April 2007), battling the title character, (Kara Zor-El). ^{[citation needed]}