Katherine Victoria Litwack was born June 13, 1986 and is known professionally as Kat Dennings.

She is an American actress, known for her starring roles as Max Black in the CBS sitcom 2 Broke Girls (2011–2017) and as Darcy Lewis in the Marvel Cinematic Universe superhero films Thor (2011) and Thor: The Dark World (2013), and the Disney+ miniseries WandaVision (2021).

She made her acting debut in 2000.

She was born in Bryn Mawr, Pennsylvania. Her mother, Ellen Judith Litwack, is a poet and speech therapist, and her father, Gerald J. Litwack, is a molecular pharmacologist, and college professor and chairman. Dennings is the youngest of five children, including an older brother, Geoffrey S. Litwack. Her family is Jewish.

Dennings was homeschooled; her only enrollment at a traditional school was for a half-day at Friends’ Central School. She graduated from high school early at age 14, and moved with her family to Los Angeles to pursue acting full time under the professional surname “Dennings”.

Dennings began her career in commercials at the age of 10. Her first acting job was an ad for potato chips. Dennings made her professional debut with an appearance on HBO’s Sex and the City in 2000, in the episode “Hot Child in the City”, playing an obnoxious 13-year-old who hires Samantha to handle publicity for her bat mitzvah. 

In February 2011, Dennings was cast in 2 Broke Girls, a CBS sitcom that follows the lives of two underemployed girls. Beth Behrs co-stars as a Manhattan heiress who lost her inheritance, while Dennings plays a tough outspoken girl from Brooklyn. Dennings liked the idea of reaching a wider audience with her work, so she accepted the role on the network sitcom. On May 12, 2017, CBS canceled the series after six seasons.

Dennings starred in the drama film To Write Love on Her Arms (originally titled Renee) in 2012, with Chad Michael Murray and Rupert Friend. She played Renee Yohe, a Florida teenager who struggled with substance abuse and self-injury, and who inspired the founding of the nonprofit organization To Write Love on Her Arms.

In mid-2012, Dennings filmed the independent feature Suburban Gothic, playing a small-town bartender.

In 2013, Dennings reprised her role as Darcy Lewis in the superhero sequel film Thor: The Dark World. She worked on the film and 2 Broke Girls at the same time, flying to London to film for six months between breaks on her CBS sitcom.

In 2018, it was announced that Dennings would star as Abby in the comedy film Friendsgiving.

Dennings starred in the Hulu comedy series Dollface, beginning in November 2019. She reprised her role of Darcy Lewis in the Marvel Cinematic Universe with a supporting role in the Disney+ superhero series WandaVision, which premiered on January 15, 2021.