Rachel Sarah Bilson (born November 13, 1981) is an American actress. She is best known as Summer Roberts on The O.C., an American television "dramedy", which focuses on the lives of the beautiful and wealthy in a gated Newport Beach community.

Bilson was born in Los Angeles, California, and is the daughter of writer/director Danny Bilson and granddaughter of director Bruce Bilson. Her stepmother is Heather Medway, an actress and the mother of Bilson's two-year-old half-sister Hattie.

She graduated from Walter Reed Middle School in 1996 and Notre Dame High School in 1999. During her time at Notre Dame, Bilson appeared in productions of Bye Bye Birdie, Once Upon a Mattress and The Crucible. In addition to her role on The O.C., she has appeared in 8 Simple Rules for Dating My Teenage Daughter, Buffy the Vampire Slayer, That '70s Show, and Punk'd after being tricked by Ashton Kutcher for the havoc caused by the dog that was also owned by O.C. co-star/boyfriend Adam Brody..

She resides in a two-bedroom condo in the Hollywood Hills that has been in her family for years with her best friend Leah. She is currently dating fellow The O.C. actor Adam Brody.

She is currently the spokesperson for Bongo jeans.

In 2005, Maxim magazine named her in the sixth spot of their annual "100 Hot List". At the 2005 Teen Choice Awards Bilson collected three awards - Choice Hottie Female, Choice TV Actress (Drama) and Best Onscreen TV Chemistry (jointly won with Adam Brody).