Katherine Marie Heigl (born November 24, 1978) is an American actress and film producer. She is possibly best known for her role as Dr. Isobel "Izzie" Stevens on ABC's medical drama Grey's Anatomy from 2005 to 2010, for which she won the Primetime Emmy Award for Outstanding Supporting Actress in a Drama Series in 2007. She has also starred in films such as Under Siege 2: Dark Territory, Knocked Up, 27 Dresses, The Ugly Truth, Killers, Life As We Know It and New Year's Eve, among others.

Heigl started her career as a child model with Wilhelmina Models before she turned her attention to acting. She made her debut in the coming-of-age film That Night. Heigl co-starred as Isabel Evans in the television series Roswell and movies including My Father the Hero before landing her break-out role in Grey's Anatomy. Heigl has established herself as a cover model appearing on numerous publications including Maxim, Vanity Fair and Cosmopolitan. Heigl is married to singer Josh Kelley, with whom she has two adopted daughters.

Heigl was born in West End, Washington, D.C., at Columbia Hospital for Women. She is the youngest of four children of Nancy (née Engelhardt), a personnel manager, and Paul Heigl, a financial executive and accountant. Her father is of German (including Swiss-German) and Irish descent, and her mother is ofGerman ancestry. Heigl was raised in The Church of Jesus Christ of Latter-day Saints. Her siblings are Meg, Jason (deceased), and Holt. Heigl lived in Virginia and then Denver, before her family settled in Connecticut; there, they moved into a large, old Victorian-style farmhouse in the wealthy town of New Canaan, where she spent most of her childhood. In 1986, her older brother Jason died of injuries suffered in a car accident, after being thrown from the back of a pickup truck while out for lunch with some of his high school classmates. Following his death, the family decided to donate his organs. Heigl was unnerved by this at the time, but later became a strong proponent of organ donation, working as a spokesperson for Donate Life America.

In June 2006, Heigl became engaged to singer Josh Kelley, whom she had met a year earlier on the set of his music video for "Only You". They chose not to live together before they were married, with Heigl later explaining, "I think I just wanted to save something for the actual marriage... I wanted there to be something to make the actual marriage different than the dating or the courtship." They were married on December 23, 2007 in Park City, Utah.

On September 9, 2009, Heigl's representative said the couple had started the process of adopting a baby girl from South Korea. Later that month, the couple adopted a baby girl they named Nancy Leigh (after Heigl's mother and sister, respectively), nicknamed Naleigh. Heigl's sister is Korean-born and was adopted before Heigl was born. The baby had to have a congenital heart defect repaired with open heart surgery before she had left Korea. Kelley and Heigl adopted a second daughter in April 2012 from the U.S., named Adalaide Marie Hope.