Ezri Dax is a fictional character who appears in the seventh and final season of the American science fiction TV series Star Trek: Deep Space Nine. Portrayed by Nicole de Boer, she is a counselor aboard the Bajoran space station Deep Space Nine. The character is a member of the Trill species, and is formed of both a host and a symbiont—referred to as Dax. Ezri was introduced to the series following the death of the previous Dax host, Jadzia at the end of season six. The producers made the decision that the new symbiont bearer would be female in order to ensure that Nana Visitor was not the only female member of the main cast. There were initial difficulties in casting, and the character changed from one intended to be "spooky" to one struggling to deal with all her previous personalities, having taken on the Dax symbiont without the usual preparation. De Boer was not considered for the part until co-producer Hans Beimler suggested that she submit an audition tape, which resulted in her meeting the producers in Los Angeles and subsequently gaining the role.

Nicole de Boer is a Canadian actress. She is best known for starring in the cult film Cube as Joan Leaven, playing Ezri Dax on the final season of Star Trek: Deep Space Nine (1998–1999), and as Sarah Bannerman on the series The Dead Zone (2002–2007). From 2016 to 2021, she had a recurring role as Becca Dorsay, ex-wife of one of the series leads on the Canadian-produced crime drama Private Eyes.