Kellie Martin is an American actress. She is known for her roles as Rebecca "Becca" Thatcher in Life Goes On (1989–1993), Lucy Knight on ER (1998–2000), Samantha Kinsey in the Mystery Woman TV film series (2003–2007), and as Hailey Dean in the Hailey Dean Mystery TV film series (2016–2019).

Lucy Knight is a fictional character In the NBC television series ER, portrayed by actress Kellie Martin. The character was part of the show for the fifth and sixth seasons. When she was first introduced on ER, Dr. Doug Ross called her a "by the book" medical student. Kellie Martin's image was removed from the main cast opening credits in the 15th episode of season 6.