Katherine Marie Heigl (born November 24, 1978) is an American actress and producer who is the wife of Josh Kelley. She is best known for her role as Isabel Evans on the WB/UPN science fiction teen drama series Roswell from 1999 to 2002, and as Dr. Isobel "Izzie" Stevens on the ABC medical drama series Grey's Anatomy from 2005 to 2010.

For Disney, she portrayed Nicole in the 1994 Touchstone Pictures film My Father the Hero and Alexia "Ally" Wheaton in the 1996 Disney Channel Original Movie Wish Upon a Star. She also played Romy in the ABC Family TV movie Romy and Michele: In the Beginning.

Outside of Disney, she is well-known for voicing Andie in The Nut Job and its sequel.