Rebecca Alie Romijn O'Connell (born November 6, 1972) is an American actress and former model. She is known for her role as Mystique in the original trilogy (2000–2006) of the X-Men film series, as Joan from The Punisher (2004) (both based on Marvel Comics), the dual roles of Laure Ash and Lily Watts in Femme Fatal (2002), and Una Chin-Riley on Star Trek: Discovery (2019) and Star Trek: Strange New Worlds (2022–present).

Her other major roles include Eve Baird on the TNT series The Librarians, voicing Lois Lane in the DC Animated Movie Universe, and as the host of the reality competition show Skin Wars. She has also had a recurring role as Alexis Meade on the television series Ugly Betty.