Helena Bonham Carter (born 26 May 1966) is an English actress best known for her roles in low-budget arthouse and independent films to large-scale Hollywood productions. She was nominated for the Academy Award for Best Actress for her role as Kate Croy in The Wings of the Dove (1997). For her role as Queen Elizabeth in The King's Speech (2010), she was nominated for the Academy Award for Best Supporting Actress and won the BAFTA Award for Best Actress in a Supporting Role. She also won the 2010 International Emmy Award for Best Actress for her role as British author Enid Blyton in the TV film Enid (2009).

Bonham Carter began her film career playing the title character in Lady Jane (1986), and playing Lucy Honeychurch in A Room with a View (1985). Her other film roles include Ophelia in Hamlet (1990), Where Angels Fear to Tread (1991), Howards End (1992), Elizabeth Lavenza in Mary Shelley's Frankenstein (1994), Woody Allen's Mighty Aphrodite (1995), Marla Singer in Fight Club (1999), Bellatrix Lestrange in the Harry Potter series (2007–11), Skynet in Terminator Salvation (2009), Miss Havisham in Great Expectations (2012), Madame Thénardier in Les Misérables (2012), the Fairy Godmother in Cinderella (2015) and Rose Weil in Ocean's 8 (2018). She has frequently collaborated with director Tim Burton; in Planet of the Apes (2001), Big Fish (2003), Corpse Bride (2005), Charlie and the Chocolate Factory (2005), Sweeney Todd: The Demon Barber of Fleet Street (2007), Dark Shadows (2012), and playing the Red Queen in Alice in Wonderland (2010) and its sequel Alice Through the Looking Glass (2016). Her other television films include A Pattern of Roses (1983), Fatal Deception: Mrs. Lee Harvey Oswald (1993), Live from Baghdad (2002), Toast (2010), and Burton & Taylor (2013). In 2018, she is set to portray Princess Margaret in the Netflix drama series The Crown.

She was made a Commander of the Order of the British Empire (CBE) in the 2012 New Year Honours list for services to drama, and in January 2014, the British prime minister, David Cameron, announced that Bonham Carter had been appointed to Britain's new national Holocaust Commission.