Emily Kathleen Anne Mortimer (born 6 October 1971) is a British actress. She began acting in stage productions and has since appeared in several film and television roles. In 2003, she won an Independent Spirit Award for her performance in Lovely and Amazing. She is also known for playing Mackenzie McHale in the HBO series The Newsroom (2012–2014). She co-created and co-wrote the series Doll & Em (2014–2015) and wrote and directed the miniseries The Pursuit of Love (2021), the latter of which earned her a nomination for the British Academy Television Award for Best Supporting Actress.

She provided the voice of Sophie in the English-language version of Howl's Moving Castle (2004), and starred in Scream 3 (2000), Match Point (2005), The Pink Panther (2006), The Pink Panther 2 (2009), Lars and the Real Girl (2007), Chaos Theory (2008), Harry Brown (2009), Shutter Island (2010), Cars 2 (2011), Hugo (2011), Mary Poppins Returns (2018), and Relic (2020).

Mortimer was born on 6 October 1971 in Hammersmith, London, to dramatist and barrister Sir John Mortimer, and his second wife, Penelope (née Gollop). She has a younger sister, Rosie; two older half-siblings, Sally Silverman and Jeremy, from her father's first marriage to author Penelope Fletcher; and a half-brother, Ross Bentley, from her father's relationship with actress Wendy Craig.

Mortimer studied at St Paul's Girls' School in west London where she appeared in several pupil productions. She went on to the University of Oxford, where she read Russian at Lincoln College where she performed in several plays and spent two terms at the Moscow Art Theatre School, studying acting. Before becoming an actress, she wrote a column for The Daily Telegraph and was screenwriter for an adaptation of Lorna Sage's memoir Bad Blood.

Mortimer performed in several plays while studying at the University of Oxford. While acting in a student production, she was spotted by a producer who later cast her as the lead in a television adaptation of Catherine Cookson's The Glass Virgin (1995). Subsequent television roles included Sharpe's Sword (1995) and Coming Home (1998). She followed this with the 1996 television film Lord of Misrule, directed by Guy Jenkin and filmed in Fowey, Cornwall.^{[citation needed]}

In 1996, Mortimer appeared as drug addict Fran in the first series of Silent Witness. In the same year, she appeared in her first feature film opposite Val Kilmer in The Ghost and the Darkness, and in the coming-of-age story The Last of the High Kings. 1997 saw Mortimer play the central character of Katherine Lacey in the pilot episode of Midsomer Murders. In 1998 she appeared as Kat Ashley in Elizabeth, and played Miss Flynn in the television mini series Cider with Rosie, which was adapted for television by her father. In 1999, she played three roles: she was the "Perfect Girl" dropped by Hugh Grant in Notting Hill; Esther in the television miniseries Noah's Ark, and the actress Angelina in Scream 3.

In 2000, Mortimer was cast as Katherine in Kenneth Branagh's musical adaptation of Love's Labour's Lost, where she met actor and future husband Alessandro Nivola. She took on her biggest role in an American film to date, playing opposite Bruce Willis in Disney's The Kid. A year later, she played aspiring actress Elizabeth in Lovely & Amazing, a comedy about the relationship between a mother and her three daughters. Mortimer said of the role, "It was a wonderful experience as an actor to have that opportunity [...] You hear this terrifying phrase, 'being in the moment.' I have no doubt that I was in that moment. [Elizabeth] was exposed and ridiculous and brave." Mortimer won an Independent Spirit Award for Best Supporting Actress for her role. In 2002, she had a major part as the assassin in The 51st State (also known as Formula 51), starring opposite Samuel L. Jackson and Robert Carlyle. The film was a critical and commercial failure.

In 2003, Mortimer appeared in Stephen Fry's British drama Bright Young Things, based on the 1930 novel Vile Bodies by Evelyn Waugh. It is about young and carefree London aristocrats and bohemians, set in the interwar period. Playing fiancée Nina Blount, Mortimer was described as "a character who gives Peter O'Toole a marvelous few minutes of playing dottiness to the hilt", by Washington Post's Stephen Hunter. Her last release of 2003 was Young Adam, in which she plays the girlfriend of a nihilistic barge worker (Ewan McGregor). Based on the novel of the same title, Mortimer's role in Young Adam garnered her acclaim; Evening Standard's critic wrote, "In a performance of naked courage, Emily Mortimer shows that she is prepared to go to extreme lengths of masochism in her depiction of a woman undone by love". Sight & Sound magazine thought the cast performances were "edgy", and Mortimer made the most out of an underwritten role. She also had a supporting part in the romantic drama The Sleeping Dictionary (2003).