Ellen Tigh is a fictional character from the 2004 Battlestar Galactica reboot series, portrayed by Kate Vernon from 2004 to 2009. She is the manipulative wife of series regular Colonel Saul Tigh during the first three seasons of the series. In season four, she is revealed to be the last of the Final Five Cylons, synthetic humanoid machines who are the precursors to the Cylon antagonists who oppose the human race throughout much of the series.

Katherine Elizabeth Vernon is a Canadian-born American actress. She is known for her roles as Lorraine Prescott on the CBS primetime soap opera Falcon Crest (1984–1985), the stuck-up and popular Benny Hanson in the comedy film Pretty in Pink (1986), Sophia in the 1992 film Malcolm X, and Ellen Tigh in the 2004 Syfy series Battlestar Galactica.