Kat Dennings was born Katherine Victoria Litwack in Bryn Mawr, Pennsylvania, near Philadelphia, to Ellen (Schatz), a speech therapist and poet, and Gerald Litwack, a molecular pharmacologist. She is the youngest of five children. Her family is of Russian Jewish descent. Kat was predominantly home-schooled, graduating at the age of fourteen. Her family subsequently moved to Los Angeles, California to support Kat acting full-time.