Thea Killen-Smith is a Canadian actress and production designer known for her work in voice acting for animated series and live-action films. She was born on July 4, 1986, in Calgary, Alberta, Canada.

Killen-Smith is primarily recognized for her contributions to the English-language adaptations of several Japanese anime series. Her most prominent voice role is Luna Yumizuki in the Cardfight!! Vanguard franchise. She provided the voice for this character in multiple installments of the series, including Cardfight!! Vanguard G Stride Gate-hen, Cardfight!! Vanguard G NEXT, and Cardfight!! Vanguard GZ. Luna Yumizuki is depicted as a young girl who learns to play the card game and is part of the idol unit Rummy Labyrinth within the series' narrative.

In addition to her work on Cardfight!! Vanguard, Killen-Smith has voiced characters in the English version of the anime World Trigger. Her roles in this series include Haruka Ayatsuji, Izuho Natsume, and Mako Hitomi. She is also credited with voicing Hanako in the Toilet for the English version of the anime Future Card Buddyfight.

Beyond anime, Thea Killen-Smith's acting credits extend to live-action projects. Her filmography includes roles in the films Legend of the Lich Lord (2015), where she played a Warrior Elf, and the science fiction film Empyrean (2016). She has also worked in the art department and as a production designer on various projects, including the film Space Rippers.