Age: 44
Nominated for: Blue Jasmine
The character: Jasmine is a wealthy New York socialite who suffers a humiliating fall from grace after her husband is arrested for financial fraud.
Oscar record: The Australian actress has picked up five previous Academy Award nominations, including two nods for the role of Elizabeth I, whom she portrayed in 1998's Elizabeth and its 2007 sequel The Golden Age. She won the best supporting actress Oscar in 2005 for playing Hollywood star Katharine Hepburn in The Aviator.
The critics said: "Blanchett, who has played Blanche in Streetcar on stage, is the film's glory. She is miraculous at finding the bruised heart of this bullying elitist. This is Blanchett triumphant, and not to be missed." Peter Travers, Rolling Stone
Age: 49
Nominated for: Gravity
The character: Dr Ryan Stone, an astronaut coping with the loss of her four-year-old daughter, is left adrift in space after a devastating accident.
Oscar record: Bullock's one previous nomination converted to an Oscar statuette for her leading role in The Blind Side in 2010.
The critics said: "Bullock inhabits the role with grave dignity and hints at Stone's past scars with sensitivity and tact, and she holds the screen effortlessly once Gravity becomes a veritable one-woman show." Justin Chang, Variety
Age: 79
Nominated for: Philomena
The character: Philomena Lee is an Irish Catholic woman who was sent to a convent when she became pregnant as a teenager in the 1950s, and saw her child given up for adoption. A meeting with a journalist in later life prompts a search to find the son she lost. Philomena Lee is still alive today.
Oscar record: Dame Judi has previously landed a total of six Academy Awards nominations. She won for her second nomination, playing Queen Elizabeth I in Shakespeare in Love. Famously, she appeared on screen for only eight minutes.
The critics said: "Ms. Dench's Philomena Lee glows with the radiance of someone serene in her faith despite inhumane treatment by the church. That she makes you believe her character has the capacity to forgive, provides the movie with a solid moral centre." Stephen Holden, New York Times
Age: 39
Nominated for: American Hustle
The character: Sydney Prosser is a confidence trickster who is forced to take part in an FBI sting operation to root out corrupt politicians.
Oscar record: Has already picked up four nominations all in the best supporting actress category, most recently for 2012's The Master - but has yet to collect a golden statuette.
The critics said: "Sydney Prosser is played with a gleam of pure self-harming passion by Amy Adams." Peter Bradshaw, The Guardian
Age: 64
Nominated for: August: Osage County
The character: Violet Weston, a family matriarch suffering from cancer with a penchant for taking prescription drugs and doling out searing insults to her loved ones.
Oscar record: Streep has collected a total of 17 nominations from previous years, with three wins. One for best supporting actress in Kramer vs Kramer (1980) and two for best actress: Sophie's Choice (1983) and, almost 30 years later, as Margaret Thatcher in The Iron Lady, in 2012.
The critics said: "There's no denying the raging force with which Meryl Streep tears into the role of Violet Weston, a Great Plains matriarch who specialises in tormenting the people around her." Owen Gleiberman, Entertainment Weekly
A look at the best actress winner and her fellow nominees at the 86th Academy Awards.