Katharine Houghton Hepburn (May 12, 1907 – June 29, 2003) was an American actress of film, stage, and television. Hepburn's career as a Hollywood leading lady spanned more than 60 years. Known for her headstrong independence and spirited personality, she cultivated a screen persona that matched this public image, and regularly played strong-willed, sophisticated women. Her work came in a range of genres, from screwball comedy to literary drama, and she received four Academy Awards for Best Actress—a record for any performer. In 1999, Hepburn was named by the American Film Institute the greatest female star of classic Hollywood cinema.

Raised in Connecticut by wealthy, progressive parents, Hepburn began to act while studying at Bryn Mawr College. Favorable reviews of her work on Broadway brought her to the attention of Hollywood. Her early years in film brought her international fame, including an Academy Award for Best Actress for her third picture, Morning Glory (1933), but this was followed by a series of commercial failures culminating in the critically lauded but commercially unsuccessful comedy Bringing Up Baby (1938). Hepburn masterminded her own comeback, buying out her contract with RKO Radio Pictures and acquiring the film rights to The Philadelphia Story, which she sold on the condition that she be the star. That comedy film was a box office success and landed her a third Academy Award nomination. In the 1940s, she was contracted to Metro-Goldwyn-Mayer, where her career focused on an alliance with Spencer Tracy, which spanned 26 years and nine movies and extended to an unacknowledged off-screen affair.

Hepburn challenged herself in the latter half of her life, as she tackled Shakespearean stage productions and a range of literary roles. She found a niche playing middle-aged spinsters, such as in The African Queen (1951), a persona the public embraced. Hepburn earned three more Oscars for her work in Guess Who's Coming to Dinner (1967), The Lion in Winter (1968), and On Golden Pond (1981). In the 1970s, she began appearing in television films, which later became the focus of her career. She made her final screen appearance at the age of 87. After a period of inactivity and ill health, Hepburn died in 2003 at the age of 96.

Hepburn famously shunned the Hollywood publicity machine and she refused to conform to society's expectations of women. She was outspoken, assertive, and athletic, and wore trousers before they were fashionable for women. She was briefly married as a young woman but thereafter lived independently. With her unconventional lifestyle and the independent characters she brought to the screen, Hepburn epitomized the "modern woman" in the 20th-century United States, and is remembered as an important cultural figure.