Kate Elizabeth Winslet (; born 5 October 1975) is an English actress. Known for her roles as headstrong and complicated women in independent films, particularly period dramas, she has received numerous accolades, including an Academy Award, a Grammy Award, two Primetime Emmy Awards, five BAFTA Awards and five Golden Globe Awards. Time magazine named Winslet one of the 100 most influential people in the world in 2009 and 2021. She was appointed Commander of the Order of the British Empire (CBE) in 2012.

Winslet studied drama at the Redroofs Theatre School. Her first screen appearance, at age 15, was in the British television series Dark Season (1991). She made her film debut playing a teenage murderess in Heavenly Creatures (1994), and went on to win a BAFTA Award for playing Marianne Dashwood in Sense and Sensibility (1995). Global stardom followed with her leading role in James Cameron's epic romance Titanic (1997), which was the highest-grossing film at the time. Winslet then eschewed parts in blockbusters in favour of critically acclaimed period pieces, including Quills (2000) and Iris (2001).

The science fiction romance Eternal Sunshine of the Spotless Mind (2004), in which Winslet was cast against type in a contemporary setting, proved to be a turning point in her career, and she gained further recognition for her performances in Finding Neverland (2004), Little Children (2006), The Holiday (2006), Revolutionary Road (2008), and The Reader (2008). For playing a former Nazi camp guard in the last, she won the BAFTA Award and the Academy Award for Best Actress. Winslet's portrayal of Joanna Hoffman in the biopic Steve Jobs (2015) won her another BAFTA Award, and she received two Primetime Emmy Awards for her performances in the HBO miniseries Mildred Pierce (2011) and Mare of Easttown (2021). In 2022, she produced and starred in the single drama "I Am Ruth", winning two BAFTA TV Awards, and played a supporting role through motion capture in Cameron's top-grossing science fiction film Avatar: The Way of Water.

For her narration of a short story in the audiobook Listen to the Storyteller (1999), Winslet won a Grammy Award. She performed the song "What If" for the soundtrack of her film, Christmas Carol: The Movie (2001). A co-founder of the charity Golden Hat Foundation, which aims to create autism awareness, Winslet has also written a book on the topic. Divorced from film directors Jim Threapleton and Sam Mendes, Winslet has been married to businessman Edward Abel Smith since 2012. She has a child from each marriage, one of whom is the actress Mia Threapleton.