Cassandra

 and its variant Cassie appears several times in the Doctor Who universe and the related real world. They are listed below in alphabetical order by surname. If no surname is available, alphabetization occurs by the disambiguation term — that is, the bit between the parentheses in a title like Waitress (Vincent and the Doctor).

As only name

 * Cassandra (Annihilation) (AUDIO: Annihilation)
 * Cassandra (Asylum of the Daleks) (TV: Asylum of the Daleks)
 * Cassandra (The Myth Makers) (TV: The Myth Makers)
 * Cassandra (The Scarlet Empress) (PROSE: The Scarlet Empress)
 * Cassandra (Wildthyme at Large) (AUDIO: Wildthyme at Large)
 * Cassandra (Who Killed Kennedy) (PROSE: Who Killed Kennedy)
 * Cassandra (Zagreus) (AUDIO: Zagreus)

As first name

 * Cassandra O'Brien.Δ17 (TV: The End of the World, New Earth)
 * Cassie Rice (TV: Dreamland)
 * Cassie Scholefield (AUDIO: Project: Twilight, AUDIO: Project: Lazarus)

As name of object, publication or other in-universe item

 * Cassandra (ship) (AUDIO: The Secret of Cassandra)
 * Cassandra (So Vile a Sin) (PROSE: So Vile a Sin)

Extra

 * Cassandra (actor), who played a Movellan Guard in TV: Destiny of the Daleks

Audio

 * The Secret of Cassandra (audio story), a Bernice Summerfield audio drama