Sandy Powell CBE RDI (born 7 April 1960) is a British costume designer. She has received numerous accolades, including three Academy Awards, three BAFTA Film Awards, and two Costume Designers Guild Awards. She has been honored with the CDG Career Achievement Award in 2010 and the BAFTA Fellowship in 2023. Powell was appointed Commander of the Order of the British Empire (CBE) in 2025.

Powell is best known for her collaborations with directors Derek Jarman, Neil Jordan, Todd Haynes and Martin Scorsese. She has received 15 nominations for the Academy Award for Best Costume Design and has won three times for Shakespeare in Love (1998), The Aviator (2004), and The Young Victoria (2009). She has also been nominated for the BAFTA Award for Best Costume Design a record 16 times and had three wins for Velvet Goldmine (1998), The Young Victoria, and The Favourite (2018).

Powell was born in London in 1960, and grew up in Brixton and Clapham. Her father worked in casinos, while her mother was a secretary. In 2023, Powell said in an interview with fashion journalist Suzy Menkes that, despite their close friendship, she was not related to fellow costume designer Anthony Powell. Information about them being cousins has falsely spread online. Powell learned to sew from her mother on a Singer sewing machine, drew pictures of clothes, designed and made outfits for her dolls, and started making her own clothes from a young age. She also developed an interest in film and theatre from an early age.

Powell attended Sydenham High School, and in 1978 she completed an art foundation course at Saint Martin's School of Art, where she became acquainted with Lea Anderson, who later became a dancer and choreographer as well as Powell's collaborator. In 1979, Powell began a BA in theatre design at the Central School of Art and Design, but left after two years before completing her degree and started working for fringe theatre companies.

After leaving Central, Powell began a working relationship with dancer and choreographer Lindsay Kemp, whom she greatly admired. She designed costumes for his productions, the first of which was the show Nijinsky at La Scala in Milan. In the early 1980s, Powell became acquainted with filmmaker Derek Jarman, who became a mentor and an influential figure in her life. Following Jarman's advice, she spent a year working on music videos. She made her entry into the film industry in 1986, designing costumes for the Jarman film Caravaggio.

In 1992, Powell achieved prominence in the period drama film Orlando, directed by Sally Potter. Operating on a limited budget, Powell created elaborate costumes for the gender-switching and time-traveling protagonist (played by Tilda Swinton), for which she received her first Academy Award nomination for Best Costume Design. Powell also began a collaboration with director Neil Jordan, which would produce a total of six films including the crime thriller The Crying Game (1992), the gothic horror film Interview with the Vampire (1994) and the period drama Michael Collins (1996).

Powell received dual nominations at the 71st Academy Awards for her two 1998 films, Velvet Goldmine and Shakespeare in Love. Echoing the contemporary tone of Shakespeare in Love, Powell opted to sacrifice historical accuracy in her costume designs but still managed to achieve "emotional accuracy", according to Salon critic Stephanie Zacharek. The detail on the costumes of Gwyneth Paltrow's Viola and the thematic significance of her costume changes were also noted as highlights of the film. For her work in the film, Powell won her first Academy Award for Best Costume Design.

Following her win at the 71st Academy Awards, Powell began her collaboration with director Martin Scorsese, starting with his 2002 epic period drama film Gangs of New York, for which she earned her 5th Oscar nomination. The two reunited for the 2004 biographical drama film The Aviator, for which Powell won her second Academy Award. Powell accepted her Oscar while wearing a dress made by her frequent collaborator, the costume cutter Annie Hadley, which was a version of a dress worn by Cate Blanchett in the film.