Jadzia Dax was a heroine introduced on the Star Trek: Deep Space Nine pilot episode Emissary.
This version of Dax was portrayed by Terry Farrell.
From a very early age Jadzia knew that she wanted to be joined, and worked very hard to become eligible to host a symbiont. To be selected to be joined was a very selective and competitive process, and Jadzia distinguished herself by earning advanced degrees in several subjects. Enrolling in Starfleet Academy in 2364, she, like Jean-Luc Picard, was a student of Richard Galen.
She was dropped from the initiate program, but deciding not to take it lying down, she reapplied to the program and became the first initiate in history to graduate after having been dropped from the program by Curzon, who had dropped her after not being able to handle his feelings for her.
In 2367 it became obvious that Curzon was dying. Jadzia requested that when the time came she be the next host for Dax, which Curzon did not object to. That time came after Curzon's health took a turn for the worse while he was vacationing on Risa. She was successfully joined with Dax not long afterwards.
Jadzia graduated the following year from Starfleet Academy in the 98th percentile. She would be posted to Deep Space Nine the following year, under the command of Dax's old friend Benjamin Sisko. She and Sisko both discovered the Bajoran Wormhole, home of the Prophets, who granted use of their shortcut to the Gamma Quadrant to Bajor and its allies.
Jadzia would go on to become an important senior staff member on DS9, becoming close friends with Odo, Kira Nerys, Julian Bashir, Miles O'Brien, and Quark. She would become especially close with the Klingon Worf after he transferred to DS9, and would eventually marry him in 2373.
Jadzia died after being attacked by Gul Dukat in 2374 in the Bajoran Temple on DS9 after she tried to stop him from releasing a Pah-wraith into a Bajoran orb. Jadzia was taken to the infirmary, where Dr. Bashir found there was little he could do for Jadzia. He removed the symbiont from Jadzia and had Dax sent on its way back to Trill. Jadzia died soon afterwards, with her husband Worf and her friend Captain Sisko at her side. The Dax symbiont was subsequently joined to Ezri Tigan on the way back to the Trill homeworld, becoming Ezri Dax in the process.