Dax is a fictional character on the television show Star Trek: Deep Space Nine.

Dax is a Trill symbiont, a very long-lived slug-shaped entity that is hosted by a succession of humanoid Trills, a process called "joining". Each of the hosts has access to the memories of the previous hosts. Two of Dax's hosts, Jadzia and Ezri, were regular characters on Deep Space Nine. Dax has had a total of ten hosts:

  1. Lela;
  2. Tobin;
  3. Audrid;
  4. Emony;
  5. Torias;
  6. Joran (Jeff Magnus McBride in episode "Equilibrium" and Leigh J. McCloskey in "Field of Fire")
  7. Curzon (Frank Owen Smith - episode "Emissary");
  8. Jadzia (Terry Farrell);
  9. Verad (John Glover - episode "Invasive Procedures")
  10. Ezri (Nicole de Boer).

In an alternate future, a descendant of Jadzia's, Yedrin (Gary Frank - episode "Children of Time"), was shown to be hosting Dax.