Profiles of the actors nominated for the Best actor award at the 79th Academy Awards, to be held at the Kodak Theatre, Los Angeles on 25 February.
LEONARDO DICAPRIO - BLOOD DIAMOND
Leonardo DiCaprio had already built an impressive reputation in such films as This Boy's Life, What's Eating Gilbert Grape and William Shakespeare's Romeo + Juliet when he shot to international fame in Titanic.
The 1997 film, which went on to win 11 Oscars, put DiCaprio firmly on the Hollywood radar.
He later starred in The Beach, Gangs of New York, Catch Me If You Can and The Aviator.
The latter earned him a best actor Oscar nomination for his portrayal of legendary director Howard Hughes.
Last year proved a busy year for DiCaprio, with roles in action drama Blood Diamond and mob thriller The Departed.
Those films saw him receive two Golden Globe nominations in the best actor in a drama category.
He also received two nominations from the Screen Actors Guild Awards - best lead actor for Blood Diamond and best supporting actor for The Departed.
Born in Los Angeles in 1974, DiCaprio began his acting career in 1990 when he was cast in the TV version of hit film Parenthood.
RYAN GOSLING - HALF NELSON
Canadian actor Ryan Gosling, 26, has been nominated for best actor for his role as a teacher who confronts his drug addiction with the help of a student in Half Nelson.
But he had already made a name for himself thanks to roles in TV shows Young Hercules and Breaker High and well-received performances in films such as The Believer and The Notebook.
Born in London, Ontario, in November 1980, Gosling was raised as a Mormon.
He started his professional career at the age of 13 alongside Britney Spears, Christina Aguilera and Justin Timberlake in The Mickey Mouse Club.
His performance in Half Nelson has seen him nominated for a Screen Actor's Guild award and win a best actor prize at the 2006 Stockholm Film Festival.
While Gosling has not had formal training as an actor, his performances have been praised as "intense" and "heartfelt".
PETER O'TOOLE - VENUS
Acting legend Peter O'Toole - best known for such films as Lawrence of Arabia, Becket, The Lion in Winter and Goodbye Mr Chips - has received his eighth best actor nomination for Venus.
He has received three Golden Globes, an Emmy and an honorary Academy Award - but has yet to win a best actor Oscar outright.
O'Toole, 74, attended the Royal Academy of Dramatic Art (RADA) in the 1950s alongside such acting greats as Albert Finney, Richard Harris and Alan Bates.
His acting career began in the theatre, with stints at the Old Vic confirming him as one of his generation's leading Shakespearean actors.
O'Toole's film break came in 1962 when he was chosen to play the lead role in Lawrence of Arabia.
His portrayal of World War One hero TE Lawrence led to his first Oscar nomination for best actor.
Six more followed, the most recent coming in 1983 for My Favourite Year.
In 2003 the Academy gifted him a Honorary Award for his lifelong contribution to film - an accolade he initially refused to accept.
But he agreed to attend that year's ceremony when he learned the Academy intended to bestow the honour whether he was there to collect it or not.
WILL SMITH - THE PURSUIT OF HAPPYNESS
Will Smith has enjoyed huge success as both a TV and film actor and a Grammy-winning rap star.
Smith was the MC of hip-hop duo DJ Jazzy Jeff & the Fresh Prince when he was cast in NBC sitcom The Fresh Prince of Bel-Air in 1990.
The show ran for six years and helped launch a film career that began with a dramatic role as a gay con man in 1993's Six Degrees of Separation.
It was his role in 1995 action film Bad Boys alongside Martin Lawrence, however, that cemented his stardom.
Roles in such blockbusters as Independence Day and Men in Black followed, though the heavily derided Wild Wild West flopped.
Smith got his career back on track with Enemy of the State, Men in Black II, Bad Boys II, Hitch and I, Robot.
He received his first Oscar nomination for his portrayal of boxer Mohammed Ali in the 2001 biopic Ali.
His music career has continued, his numerous hit singles including the theme song to Men in Black and a cover of Just the Two of Us.
Willard Christopher Smith Jr was born in September 1968 in Philadelphia.
His 1997 marriage to actress Jada Pinkett has produced two children: Jaden Christopher Syre - his co-star in The Pursuit of Happyness - and Willow Camille Reign.
He also has a son, Willard Christopher III, from a previous marriage.
FOREST WHITAKER - THE LAST KING OF SCOTLAND
US actor Forest Whitaker has won plaudits for his role as Ugandan dictator Idi Amin in The Last King of Scotland.
Prior to his best actor Oscar nomination, Whitaker won a Golden Globe for best actor in a drama and received top honours from the New York Film Critics Circle, the Los Angeles Film Critics Association, the National Board of Review and the Broadcast Film Critics Association.
The 46-year-old made one of his first appearances in 1982's Fast Times at Ridgemont High, alongside Nicolas Cage and Sean Penn.
Roles in such acclaimed films as Platoon, Good Morning Vietnam and The Color of Money followed.
In 1988 he played jazz musician Charlie Parker in Bird, directed by fellow Oscar nominee Clint Eastwood.
He was named best actor at the Cannes Film Festival and nominated for a Golden Globe award.
In Britain, however, he is perhaps best known for playing IRA hostage Jody in 1992's The Crying Game.
Recent films have included Panic Room and Phone Booth, both in 2002.
Whitaker branched out into producing and directing in the 1990s, notably with Waiting to Exhale starring singer Whitney Houston in 1995.
His TV roles have included police drama The Shield and medical soap ER.
Whitaker married actress Keisha Whitaker in 1996. He has two daughters with her, a son from a previous relationship and a stepdaughter.