Performance by an Actress in a Leading Role is one of the Academy Awards of merit presented annually by the Academy of Motion Picture Arts and Sciences (AMPAS) to recognize an actress who has delivered an outstanding performance while working within the film industry. Prior to the 49th Academy Awards ceremony (1976), this award was simply known as the Academy Award of Merit for Performance by an Actress. Since its inception, however, the award has commonly been referred to as the Oscar for Best Actress. While actresses are nominated for this award by Academy members who are actors and actresses themselves, winners are selected by the Academy membership as a whole.

Throughout the past 84 years, accounting for ties and repeat winners, AMPAS has presented a total of 85 Best Actress awards to 70 different actresses. Winners of this Academy Award of Merit receive the familiar Oscar statuette, depicting a gold-plated knight holding a crusader's sword and standing on a reel of film. The first recipient was Janet Gaynor, who was honored at the 1st Academy Awards ceremony (1929) for her performances in Seventh Heaven, Street Angel, and Sunrise. The most recent recipient was Meryl Streep, who was honored at the 84th Academy Awards ceremony (2012) for her performance in The Iron Lady.

Best Actress is the name of an award which is presented by various film, television and theatre organizations, festivals, and people's awards. It may refer to:

An Academy Award is an award bestowed by the American Academy of Motion Picture Arts and Sciences (AMPAS) to recognize excellence of professionals in the film industry, including directors, actors and writers. The Oscar statuette is officially named the Academy Award of Merit and is one of nine types of Academy Awards.

The formal ceremony at which the Awards of Merit are presented is one of the most prominent award ceremonies in the world, and is televised live in more than 100 countries annually. It is also the oldest award ceremony in the media; its equivalents, the Grammy Awards (for music), Emmy Awards (for television), and Tony Awards (for theatre) are modeled after the Academy.

The AMPAS was originally conceived by Metro-Goldwyn-Mayer studio boss Louis B. Mayer as a professional honorary organization to help improve the film industry’s image and help mediate labor disputes. The Oscar itself was later initiated by the Academy as an award "of merit for distinctive achievement" in the industry.

Sandra Annette Bullock ( /ˈbʊlək/; born July 26, 1964) is an American actress and producer who rose to fame in the 1990s after roles in successful films such as Demolition Man, Speed, The Net, A Time to Kill, and While You Were Sleeping. In the new millennium she appeared in such films as Miss Congeniality, The Lake House, and Crash, the third of which received critical acclaim. In 2007, she was ranked as the 14th richest female celebrity with an estimated fortune of US$85 million. In 2009, Bullock starred in two of the more financially successful films of her career, The Proposal and The Blind Side. Bullock was awarded a Golden Globe Award for Best Actress, a Screen Actors Guild Award for Outstanding Performance by a Female Actor in a Leading Role, and the Academy Award for Best Actress, for her role as Leigh Anne Tuohy in The Blind Side. She is listed in the 2012 edition of the Guinness Book Of World Records as the highest-paid actress, with $56 million.

Sandra Annette Bullock was born in Arlington, Virginia, a suburb of Washington, D.C. Her father, John W. Bullock (born 1925), was a United States Army employee and part-time voice coach from Birmingham, Alabama, and her mother, Helga D. Meyer (1942–2000), was a German opera singer and voice teacher. Bullock's maternal grandfather was a rocket scientist from Nuremberg, Germany. John Bullock, then in charge of the Army's Military Postal Service in Europe, was stationed in Nuremberg when he met his wife. They married in Germany, soon moving to Arlington, where John Bullock worked with the Army Materiel Command, before becoming a contractor for The Pentagon.

Jennifer Shrader Lawrence (born August 15, 1990) is an American film and television actress. She had lead roles in TBS's The Bill Engvall Show and in the independent films The Burning Plain and Winter's Bone, for which she received nominations for the Academy Award, Golden Globe Award, Satellite Award, and the Screen Actors Guild Award. At age 20, she was the second youngest actress ever to be nominated for the Academy Award for Best Actress. She is also known for playing Mystique in X-Men: First Class. In 2012, Lawrence achieved wider recognition starring as the heroine Katniss Everdeen in The Hunger Games, an adaptation of Suzanne Collins' best-selling novel of the same name. Her performance in the film garnered her notable critical praise and marked her as the highest grossing action heroine of all time. Lawrence's performances thus far have prompted Rolling Stone to define her as "the most talented young actress in America."

Lawrence was born and raised in Louisville, Kentucky, and has two older brothers. Her parents are Karen (née Koch), who runs a children's camp, and Gary Lawrence, who once owned a concrete construction firm, Lawrence & Associates. She acted in local theater and, by the age of 14, had decided to pursue an acting career, persuading her parents to take her to New York City to find a talent agent. Prior to finding success in Hollywood, Lawrence attended Kammerer Middle School. She graduated from high school two years early with a 3.9 average in order to begin a career in acting. While growing up and in between acting, Lawrence served as an assistant nurse at the children's summer day camp that her mother ran.