Jennifer Lynn Connelly (born December 12, 1970) is an American actress. She began her career as a child model before making her acting debut in the 1984 crime film Once Upon a Time in America. After a few more years of modeling, she began to concentrate on acting, starring in a variety of films including the horror film Phenomena (1985), the musical fantasy film Labyrinth (1986), the romantic comedy Career Opportunities (1991), and the period superhero film The Rocketeer (1991). She received praise for her performance in the science fiction film Dark City (1998) and playing a drug addict in Darren Aronofsky's drama film Requiem for a Dream (2000).

Connelly won the Academy Award for Best Supporting Actress for her portrayal of Alicia Nash in the John Nash biopic A Beautiful Mind (2001), directed by Ron Howard. Her subsequent films include the superhero film Hulk (2003), the drama House of Sand and Fog (2003), the horror film Dark Water (2005), the psychological drama Little Children (2006), the thriller Blood Diamond (2006), the science fiction film The Day the Earth Stood Still (2008), and the romantic comedy He's Just Not That Into You (2009). In the subsequent decades, she took on supporting roles in Aronofsky's biblical epic film Noah (2014) and in the action films Alita: Battle Angel (2019) and Top Gun: Maverick (2022). She also starred in the science fiction television series Snowpiercer (2020–2024) and Dark Matter (2024).

Connelly was named Amnesty International Ambassador for Human Rights Education in 2005. She has been the face of Balenciaga and Louis Vuitton fashion advertisements, as well as for Revlon cosmetics. In 2012, she was named the first global face of the Shiseido Company. Magazines, including Time, Vanity Fair, and Esquire, as well as the Los Angeles Times newspaper, have included her on their lists of the world's most beautiful women.

Jennifer Lynn Connelly was born on December 12, 1970, in Round Top, a hamlet in the town of Cairo, New York, United States. She is the only child of Ilene Carol (née Schumann; 1942–2013), an antique dealer, and Gerard Connelly (died 2008), a clothing manufacturer. Ilene was Jewish and was educated at a yeshiva, while Gerard was a Catholic of Irish and Norwegian descent. Ilene's ancestors were Jewish emigrants from Poland and Russia. The family moved to the neighborhood of Brooklyn Heights, New York City, when Connelly was one year old, and she attended Saint Ann's School. Gerard suffered from asthma, so the family moved to the town of Woodstock in 1976 to escape the city smog. Four years later, they returned to Brooklyn Heights, and Connelly returned to Saint Ann's School.

After graduating from high school in 1988, Connelly went to Yale University to study English literature. Connelly has described herself as a conscientious student who "wasn't really concerned with having a social life or sleeping or eating much. I was really nerdy and pretty much stayed in the law school library, which is open 24 hours, most of the time I wasn't in class." After two years at Yale, she transferred to Stanford University to study drama. There, she trained with Roy London, Howard Fine, and Harold Guskin. Encouraged by Ilene and Gerard to continue with her film career, Connelly left college and returned to the film industry the same year. Ilene and Gerard divorced in 2000.

When Connelly was ten years old, an advertising executive friend of her father suggested she audition as a model. Her parents sent a picture of her to the Ford Modeling Agency, which shortly after added her to its roster. Connelly began modeling for print advertisements before moving on to television commercials. In an interview with The Guardian from 2002, she revealed that, after having done some modeling, she had no aspirations to become an actress. She appeared on the covers of several issues of the American teenage magazine Seventeen in 1986 and 1988. In December 1986, she recorded two pop songs for the Japanese market: "Monologue of Love" and "Message of Love". She sang in phonetic Japanese as she did not speak the language.

When her mother began taking her to acting auditions, a then 11 year-old Connelly was quickly selected for a supporting role as the aspiring dancer and actress Deborah Gelly in Sergio Leone's Jewish gangster epic Once Upon a Time in America (filmed 1982–83, released 1984). The role required her to perform a ballet routine. During the audition, Connelly, who had no ballet training, tried to imitate a ballerina. Her performance, and the similarity of her nose to Elizabeth McGovern's, who played the character as an adult, convinced the director to cast her. Connelly described the film as "an incredibly idyllic introduction to movie-making".

Connelly's first leading role was in Italian giallo-director Dario Argento's 1985 film Phenomena. In the film, she plays a girl who psychically communicates with insects to pursue the killer of students of the Swiss school where she has enrolled. During filming, she was attacked by a chimpanzee and was bitten on the finger. Connelly next had the lead in the coming-of-age film Seven Minutes in Heaven, released the same year. In a retrospective interview, Connelly said, "Before I knew it, [acting] became what I did. It was a very peculiar way to grow up, combined with my personality." She described feeling like "a kind of walking puppet" through her adolescence, without having time alone to deal with the attention her career was generating.