Margo Martindale was born July 18, 1951 in Jacksonville, Texas to parents William Everett and Margaret (Pruitt) Martindale. In addition to owning and operating a lumber company in Jacksonville, her father was known as a champion dog handler in Texas and throughout the southern United States. Margo was the youngest of three children and only daughter. Her oldest brother is professional golfer and golf course designer Billy Martindale. Middle child, brother Bobby Tim, died in 2004. Margo Martindale participated in golf, cheerleading and drama while in school and was crowned "Football Sweetheart" as well as "Miss Jacksonville High School 1969." Following graduation from Jacksonville High School in 1969, Martindale attended Lon Morris College then transferred to the University of Michigan at Ann Arbor. While at Michigan, she also did summer study at Harvard University, appearing onstage with future movie and TV stars Jonathan Frakes and Christopher Reeve.
Her film roles include turns as Susan Sarandon's fellow nun in Dead Man Walking, and, again with Sarandon, in Lorenzo's Oil. She appeared as Leonardo DiCaprio's doctor in Marvin's Room; and as Hilary Swank's selfish mother in Million Dollar Baby. Other films include The Human Stain with Anthony Hopkins and Nicole Kidman, 28 Days with Sandra Bullock, Proof of Life with Russell Crowe and Meg Ryan and Practical Magic again with Nicole Kidman and Sandra Bullock. She was also featured in Paris, je t'aime, starring in the final segment directed by Alexander Payne. She played Mama Cox in the 2007 film Walk Hard and played Ruby, Miley Cyrus' maternal grandmother, in Hannah Montana: The Movie. Her most recent role was as Miss Elizabeth Ham in the movie Secretariat, starring Diane Lane.
One of Martindale's first television roles came in the miniseries Lonesome Dove. A series of character and guest appearances followed in a wide diversiy of TV shows. Martindale played recurring character Camilla Figg on the first three seasons of Dexter and had a recurring role in the A&E courtroom drama 100 Centre Street with Alan Arkin. In 2007-2008, she had a recurring role as Nina Burns, a neighbor of the Malloy/"Rich" family in The Riches with Minnie Driver and Eddie Izzard. Martindale joined the cast of Justified for the second season. She played the role of Mags Bennett, matriarch of the Bennett crime family which controlled much of the drug activity in the fictional version of Harlan County, Kentucky. Her role as Mags won her the Primetime Emmy Award for Outstanding Supporting Actress in a Drama Series in 2011.