Kat Dennings was born Katherine Litwack in Bryn Mawr, Pennsylvania, near Philadelphia, to Ellen (Schatz) and Gerald Litwack. She is the youngest of five children.
Kat was predominantly home-schooled, graduating at the age of 14. Her family subsequently moved to Los Angeles, California to support Kat acting full-time.
After work doing commercials, she began work in television, starting with a role on HBO's Sex and the City (1998), following up with roles on Raising Dad (2001), The Scream Team (2002), Everwood (2002), Without a Trace (2002) and ER (1994), among others.
Kat made the move to the big screen with supporting roles in Raise Your Voice (2004), The 40-Year-Old Virgin (2005) and Big Momma's House 2 (2006). She later achieved a level of fame with roles in The House Bunny (2008) and Nick and Norah's Infinite Playlist (2008).
Kat continues to act in feature films and is an avid video blogger.