- For the mirror universe counterpart, see Wu (mirror Ensign).
- For other uses, see Wu.
Ensign Wu was a Human woman who lived during the 23rd century. She served in Starfleet as a security officer aboard the USS Enterprise under Captain James T. Kirk.
In 2270, a newly-arrived ensign had met Wu and knew she was a dead shot in combat.
Shortly afterward, Spock and the ensign accidentally time traveled sideways into the Mirror Universe and materialized aboard the ISS Enterprise. The ensign spotted Wu's counterpart in a corridor and recalled Wu — he assumed her counterpart would have similar marksmanship skills. (TOS novella: Voyage to Adventure)