Marg Helgenberger is an American actress best known for her role as Catherine Willows in the CBS crime drama series CSI: Crime Scene Investigation. She has won numerous awards for her performance, including a Primetime Emmy Award and a Golden Globe Award. Helgenberger began her career in the early 1980s, appearing in several television series and films. She is also known for her roles in the films Species, Erin Brockovich, and Mr. Brooks.