Marg Helgenberger is an American actress best known for her role as Catherine Willows in the CBS drama series CSI: Crime Scene Investigation. She has also appeared in films such as Species, Erin Brockovich, and Mr. Brooks. Helgenberger began her career in the early 1980s with a role in the soap opera Ryan's Hope. She has since gone on to win numerous awards, including an Emmy Award and two Golden Globe nominations.