She was born as Lucile Vasconcellos Langhanke in Quincy, Illinois. Astor was the only child of Otto Ludwig Langhanke (October 2, 1871 – February 3, 1943) and Helen Marie de Vasconcellos (April 19, 1881 – January 18, 1947) who were both teachers.

Her father, who was born in Berlin, emigrated to the United States from Germany in 1891 and became a naturalized citizen; her mother was born in Jacksonville, Illinois, of Portuguese and Irish extraction. They married on August 3, 1904 in Lyons, Kansas. Otto was a German teacher at Quincy High School until the U.S. entered World War I. He then began doing light farming. Helen, who had always wanted to be an actress, began teaching drama and elocution.

Lucile was home-schooled in academics and taught to play the piano by her father, who insisted she practice daily (this talent came in handy later when she played piano in her films "The Great Lie" and "Meet Me In St. Louis"). In 1919, she sent a photograph of herself to a beauty contest in Motion Picture Magazine and became a semifinalist. Her father then moved the family to Chicago, where he took a position teaching German in public schools. Lucile took drama lessons and appeared in various amateur stage plays.

The following year, she sent another photograph to the magazine and this time became a finalist, this time being named runner-up in the national contest. Her father then moved the family to New York, in order for his pretty daughter to become an actress in motion pictures. He managed all her affairs from September 1920 to June 1930.

A Manhattan photographer, Charles Albin, saw a photograph and asked the young girl with haunting eyes and long auburn hair, whose nickname was "Rusty," to pose for him. The Albin photographs were seen by Harry Durant of Famous Players-Lasky and Lucile was signed to a six-month contract with Paramount Pictures. Her name was changed to Mary Astor during a conference between Paramount chief Jesse Lasky, gossip columnist Louella Parsons, and producer Walter Wanger.

Astor made her debut in the 1920 film The Scarecrow. At age 14, she appeared in the 1921 film Sentimental Tommy, but her small part in a dream sequence wound up on the cutting room floor. Paramount let her contract lapse. She then appeared in some movie shorts with sequences based on famous paintings. She received critical recognition for the 1921 two-reeler The Beggar Maid. Her first feature-length movie was John Smith (1922), which was followed that same year by The Man Who Played God. In 1923, she and her parents moved to Hollywood.

After appearing in several larger roles at various studios, she was signed by Paramount again, this time to a one-year contract at $500 a week. She had appeared in several more movies when John Barrymore saw a photograph of her in a magazine and wanted her cast in his upcoming movie. On loan-out to Warner Bros., she starred with him in Beau Brummel (1924). The older actor wooed the young actress, but their relationship was severely constrained by Astor's parents' unwillingness to let the couple spend time alone together. It was only because Barrymore convinced the Langhankes that his acting lessons required privacy that the couple managed to be alone at all. Their secret engagement ended largely because of the Langhankes' interference and Astor's inability to escape their heavy-handed authority, but also because Barrymore became involved with Astor's fellow WAMPAS Baby Star Dolores Costello, whom he later married.

In 1925, Astor's parents bought a Moorish style mansion with of land known as "Moorcrest" in the hills above Hollywood. The Langhankes not only lived lavishly off Astor's earnings, but kept her a virtual prisoner inside Moorcrest. Moorcrest is notable not only for its ornate style, but its place as the most lavish residence associated with the Krotona Colony, a utopian society founded by the Theosophical Society in 1912. Built by Marie Russak Hotchener, a Theosophist with no formal architectural training, the house combines Moorish and Mission Revival styles and contains such Arts and Crafts features as art glass windows (whose red lotus design Astor called "unfortunate"), and Batchelder tiles. Moorcrest, which recently has undergone a multi-million-dollar renovation, is still standing. Before the Langhankes bought it, it was rented by Charlie Chaplin, whose tenure is memorialized by an art glass window featuring the Little Tramp.

Astor's parents were not Theosophists, though the family was friendly with both Marie Hotchener and her husband Harry, both prominent TS members. Marie Hotchener was the person who negotiated Astor's right to a $5 a week allowance (at a time when she was making $2500 a week) and the right to go to work unchaperoned by her mother. The following year when she was 19, Astor, fed up with her father's constant physical and psychological abuse as well as his control of her money, climbed from her second floor bedroom window and escaped to a hotel in Hollywood, as recounted in her memoirs. Hotchener facilitated her return by persuading Otto Langhanke to give Astor a savings account with a $500 and the ability to come and go as she pleased. Nevertheless, she did not gain control of her salary until she was 26 years old, at which point her parents sued her for financial support. Astor settled the case by agreeing to pay her parents $100 a month. Otto Langhanke put Moorcrest up for auction in the early 1930s, hoping to get more than the $80,000 he had been offered for it; it went for $25,000.

Astor went on appearing in movies at various studios. When her Paramount contract ended in 1925, she was signed at Warner Bros. Among her assignments was another role with John Barrymore, this time in Don Juan (1926). She was named one of the WAMPAS Baby Stars in 1926, along with Mary Brian, Dolores Costello, Joan Crawford, Dolores del Río, Janet Gaynor, and Fay Wray.

On loan to Fox Film Corporation, Astor starred in Dressed To Kill (1928), which received good reviews. That same year, she starred in the sophisticated comedy Dry Martini at Fox. She later said that, while working on the latter, she "absorbed and assumed something of the atmosphere and emotional climate of the picture." She said it offered "a new and exciting point of view; with its specious doctrine of self-indulgence, it rushed into the vacuum of my moral sense and captivated me completely." When her Warner Bros. contract ended, she signed a contract with Fox for $3,750 a week.

In 1928, she married director Kenneth Hawks at her family home, Moorcrest. He gave her a Packard automobile as a wedding present and the couple moved into a home high up on Lookout Mountain in Los Angeles above Beverly Hills.

As the movie industry made the transition to talkies, Fox gave her a sound test, which she failed because the studio found her voice to be too deep. Though this was probably due to early sound equipment and the inexperience of technicians, the studio released her from her contract and she found herself out of work for eight months in 1929.

Astor took voice training and singing lessons during her time off, but no roles were offered. Her acting career was then given a boost by her friend, Florence Eldridge (wife of Fredric March), whom she confided in. Eldridge, who was to star in the stage play Among the Married at the Majestic Theatre in Downtown Los Angeles, recommended Astor for the second female lead. The play was a success and her voice was deemed suitable, being described as low and vibrant.

She was happy to be back at work, but her happiness soon ended. On January 2, 1930, while filming sequences for the Fox movie Such Men Are Dangerous, Kenneth Hawks was killed in a mid-air plane crash over the Pacific. Astor had just finished a matinee performance at the Majestic when Florence Eldridge came to her with the news. She was rushed from the theatre and taken to Eldridge's apartment; a replacement, Doris Lloyd, stepped in for the next show. Astor remained with her friend, Eldridge, at her apartment for some time, but she soon went back to work. Shortly after her husband's death, she debuted in her first "talkie", Ladies Love Brutes (1930) at Paramount, which co-starred friend Fredric March.

While her career picked up, her private life remained difficult. After working on several more movies, she suffered delayed shock over her husband's death and had a nervous breakdown. During the months of her illness, she was attended to by Dr. Franklyn Thorpe, whom she married on June 29, 1931.

In May 1932, the Thorpes purchased a yacht and sailed to Hawaii. Astor was expecting a baby in August, but gave birth in June in Honolulu. The child, a daughter, was named Marylyn Hauoli Thorpe: her first name combined her parents' names and her middle name is Hawaiian.

When they returned to Southern California, Astor freelanced and gained the pivotal role of Barbara Willis in MGM's Red Dust (1932) with Clark Gable and Jean Harlow. In late 1932 though, Astor signed a featured player contract with Warner Bros. Meanwhile, besides spending lavishly, her parents invested in the stock market, which turned out in many instances to be unprofitable. They still lived in Moorcrest, Astor had dubbed it a "white elephant", and she refused to maintain the house. She had to turn to the Motion Picture Relief Fund in 1933 to pay her bills.

In 1933, she appeared as the female lead, Hilda Lake, the niece of the murder victims, in The Kennel Murder Case, co-starring with William Powell playing detective Philo Vance. Film critic William K. Everson pronounced it a "masterpiece" in the August 1984 issue of Films in Review. Unhappy with her marriage, she took a break from movie making in 1933 and went to New York by herself. While there, enjoying a whirlwind social life, she met the playwright George Kaufman and they had an affair, which she documented in her diary.

A legal battle drew press attention on Astor in 1936. Dr. Franklyn Thorpe divorced Astor in 1935 and a custody battle resulted over their four year old daughter, Marylyn. Thorpe threatened to use Astor's diary in the proceedings, which told of her affairs with many celebrities, including George S. Kaufman. The diary was never offered as evidence during the trial, but Thorpe and his lawyers constantly used it as evidence. Astor maintained that the diary entries were forgeries but later acknowledged that the Kaufman entries were real. A judge later ordered the diary sealed and impounded.

Astor had just begun work on Dodsworth as news of the diary became public. Producer Samuel Goldwyn was urged to fire her, as her contract had a morality clause, but Goldwyn refused and the movie went on to be a hit.

Ultimately, the scandals caused no harm to Astor's career, which was actually revitalized because of the custody fight and the huge amount of publicity it generated; Dodsworth (1936), with Walter Huston, was released to rave reviews, and the public's acceptance assured the studios that she was still a viable commercial property.

In 1937, she returned to the stage in a well-received productions of Noel Coward's 30, The Astonished Heart, and Still Life. She also began performing regularly on radio. Some of her best movies were still to come, including The Prisoner of Zenda (1937), John Ford's The Hurricane (1937), and Brigham Young (1940).

In John Huston's The Maltese Falcon (1941), Astor was cast in her best known role as Brigid O'Shaughnessy, the scheming temptress who is eventually revealed to have murdered Sam Spade's partner, Miles Archer. The film also starred Humphrey Bogart, with Peter Lorre and Sydney Greenstreet.

Another noteworthy performance was her Oscar-winning role as Sandra Kovak, the selfish, self-centered concert pianist, who willingly gives up her child, in The Great Lie (1941). George Brent played her intermittent love interest, but the film's star was Bette Davis. Davis wanted Astor cast in the role after watching her screen test and seeing her play Tchaikovsky's Piano Concerto No. 1. She then recruited Astor to collaborate with her on rewriting the script, which Davis felt was mediocre and needed work to make it more interesting. Astor further followed Davis's advice and sported a brazenly bobbed hairdo for the role.

The soundtrack of the movie during the scenes where she plays the concerto, with violent hand movements on the piano keyboard, was actually dubbed by pianist Max Rabinovitch. Davis deliberately stepped back to allow Astor to shine in her key scenes. As a result of her performance, Astor won the Academy Award for Best Supporting Actress, thanking Bette Davis and Tchaikovsky in her acceptance speech. Astor and Davis became good friends.

Astor was not propelled into the upper echelon of movie stars by these successes, however. She always declined offers of starring in her own right. Not wanting the responsibility of top billing and having to "carry the picture," she preferred the security of being a featured player.

In 1942 she was reunited with Humphrey Bogart and Sydney Greenstreet in John Huston's Across the Pacific. She also played the Princess Centimillia in the Preston Sturges film, The Palm Beach Story (1942) for Paramount.

In February 1943, Astor's father, Otto Langhanke, died in Cedars of Lebanon Hospital as a result of a heart attack complicated by influenza. His wife and daughter were both at his bedside.

That same year, Astor signed a seven-year contract with MGM, which turned out to be a regrettable mistake. She was kept busy playing what she considered mediocre mother roles. After Meet Me In St. Louis (1944), the studio allowed her to make her Broadway debut in Many Happy Returns (1945). The play was a miserable failure, but Astor received good reviews.

On loan-out to 20th Century Fox, she played a wealthy widow in Claudia and David (1946). She was also loaned to Paramount to play Fritzi Haller in Desert Fury (1947) in which she played the tough owner of a saloon and casino in a small mining town.

Before Helen Langhanke died of a heart ailment in January 1947, Astor said she sat in the hospital room with her mother, who was delirious and did not know her, and listened quietly as Helen told her all about terrible, selfish Lucile. After her death, Astor said she spent countless hours copying her mother's diary so she could read it and was surprised to learn how much she was hated.

Back at MGM, Astor went on being cast in undistinguished, colorless mother roles. One exception was when she played a prostitute in the film noir Act of Violence (1948). The last straw came when she was cast as Marmee March in Little Women (1949). Astor found no redemption in playing what she considered another humdrum mother and became despondent. The studio wanted to renew her contract, promising to give her better roles, but she declined the offer.

At the same time, Astor's drinking was getting much worse. She admitted to having a problem with alcohol as far back as the 1930s, but it had never interfered with her work schedule or performance. She hit bottom in 1949 and went into a sanitarium for alcoholics.

In 1951, she made a frantic call to her doctor and told him she had taken too many sleeping pills. She was taken to a hospital and the police reported that she had attempted suicide, this being her third overdose in two years, and the story made headline news. She maintained it had been an accident.

That same year, she joined Alcoholics Anonymous and converted to Roman Catholicism. She credited her recovery to a priest, Peter Ciklic, also a practicing psychologist, who encouraged her to write about her experiences as part of therapy. She also separated from her fourth husband, Thomas Wheelock (a stockbroker she had married on Christmas Day 1945), but did not actually divorce him until 1955.

In 1952, she was cast in the leading role of the stage play Time of the Cuckoo, which was later made into the movie Summertime (1955), and subsequently toured with it. After the tour, Astor lived in New York for four years and worked in the theatre and on television.

Her TV debut was in The Missing Years (1954) for Kraft Television Theatre. She acted frequently in TV during the ensuing years and appeared on most of the big shows of the time, including The United States Steel Hour, Alfred Hitchcock Presents, Rawhide, Dr. Kildare, Burke's Law, and Ben Casey. She also starred on Broadway in The Starcross Story (1954), which was another failure.

She returned to Southern California in 1956. She then went on a successful theatre tour of Don Juan in Hell directed by Agnes Moorehead and co-starring Ricardo Montalban.

Astor's memoir, My Story: An Autobiography, was published in 1959, becoming a sensation for its day and a bestseller. It was the result of Father Ciklic urging her to write. Though she spoke of her troubled personal life, her parents, her marriages, the scandals, her battle with alcoholism, and other things about her life, she did not mention the movie industry or her career in any detail. In 1971, another book was published, A Life on Film, where she discussed her career. It too became a bestseller. Astor also tried her hand at fiction, writing the novels The Incredible Charley Carewe (1960), The Image of Kate (1962), The O'Conners (1964), Jahre und Tage (1964) (a German translation of The Image of Kate), Goodbye, Darling, be Happy (1965), and A Place Called Saturday (1968).

She appeared in several movies during this time, including A Stranger in My Arms (1959). She made a comeback in Return to Peyton Place (1961) playing Roberta Carter, the domineering mother who insists the "shocking" novel written by Allison Mackenzie should be banned from the school library, and received good reviews for her performance.

After taking a trip around the world in 1964, Astor was lured away from her Malibu home, where she was spending time gardening and working on her third novel, to make what she decided would be her final movie appearance.

When she was offered the small role as a key figure in the murder mystery Hush... Hush, Sweet Charlotte, starring her friend Bette Davis, Astor decided it would serve as her swan song in the movie business. After 109 movies during a career spanning 45 years, she turned in her Screen Actors Guild card and retired.

She later moved to Fountain Valley, California, where she lived near her son, Tono del Campo (from her (third) marriage to Mexican-born film editor Manuel del Campo) and his family, until 1971. That same year, suffering from a chronic heart condition, she then moved to a small cottage on the grounds of the Motion Picture & Television Country House, the industry's retirement facility in Woodland Hills, where she had her own private table when she chose to eat in the resident dining room.

In 1980, she appeared in the television documentary series A Celebration of the American Silent Film, produced by Kevin Brownlow, in which she discussed her roles during the silent film period.

Astor died on September 25, 1987, at age 81, of respiratory failure due to pulmonary emphysema while a patient in the hospital in the Motion Picture House complex. She is interred in Holy Cross Cemetery, Culver City.

Mary Astor has a star on the Hollywood Walk of Fame at 6701 Hollywood Boulevard in Hollywood.

|-| 1920| The Scarecrow| Bit Part||-|rowspan="7"|1921|Wings of the Border| Bit Part||-|The Beggar Maid| Peasant Girl / Beggar Maid||-|My Lady o' the Pines| Bit Part||-|Sentimental Tommy| Bit Part||-|Brother of the Bear| Bit Part||-|The Bashful Suitor| Bit Part||-|Bullets or Ballots| Bit Part||-|rowspan="6"|1922|The Rapids| Elsie Worden||-|The Man Who Played God|Young Woman||-|Hope|Hope||-|John Smith|Irene Mason||-|The Young Painter| Bit Part||-|The Angelus| Bit Part||-|rowspan="8"|1923|To the Ladies| Bit Part||-|Woman-Proof|Violet Lynwood||-|The Marriage Maker|Vivian Hope-Clarke||-|Puritan Passions|Rachel||-|The Bright Shawl|Narcissa Escobar||-|Success|Rose Randolph||-|Hollywood|Herself (cameo)||-|Second Fiddle|Polly Crawford||-|rowspan="6"|1924|Inez from Hollywood|Fay Bartholdi||-|The Price of a Party|Alice Barrows||-|Unguarded Women|Helen Castle||-|The Fighting American|Mary O'Mallory||-|Beau Brummel|Lady Margery Alvanley||-|The Fighting Coward|Lucy||-|rowspan="6"|1925|Scarlet Saint|Fidele Tridon||-|The Pace That Thrills|Doris||-|Don Q Son of Zorro|Dolores de Muro||-|Playing with Souls|Margo||-|Enticement|Leonore Bewlay||-|Oh, Doctor!|Dolores Hicks||-|rowspan="4"|1926|Forever After|Jennie Clayton||-|Don Juan|Adriana della Varnese||-|The Wise Guy|Mary||-|High Steppers|Audrey Nye||-|rowspan="6"|1927|No Place to Go|Sally Montgomery||-|The Rough Riders|Dolly||-|Rose of the Golden West|Elena||-|Two Arabian Knights|Mirza||-|The Sunset Derby|Molly Gibson||-|The Sea Tiger|Amy Cortissos||-|rowspan="6"|1928|Romance of the Underworld|Judith Andrews||-|Dry Martini|Elizabeth Quimby||-|Heart to Heart|Princess Delatorre/Ellen Guthrie||-|Three-Ring Marriage|Anna||-|Dressed to Kill|Jeanne||-|Sailors' Wives|Carol Trent||-|rowspan="2"|1929|The Woman from Hell|Dee Renaud||-|New Year's Eve|Marjorie Ware||-|rowspan="4"|1930|The Lash|Rosita Garcia||-|Holiday |Julia Seton||-|Ladies Love Brutes|Mimi Howell||-|The Runaway Bride|Mary Gray, AKA Sally Fairchild||-|rowspan="7"|1931|Men of Chance|Martha Silk||-|Smart Woman|Mrs. Nancy Gibson||-|White Shoulders|Norma Selbee|Lost film|-|The Sin Ship|Frisco Kitty||-|Behind Office Doors|Mary Linden||-|Other Men's Women|Lily Kulper||-|The Royal Bed|Princess Anne||-|rowspan="4"|1932|Red Dust|Barbara Willis||-|A Successful Calamity|Emmy 'Sweetie' Wilton||-|Those We Love|May Ballard||-|The Lost Squadron|Follette Marsh||-|rowspan="5"|1933|Convention City|Arlene Dale||-|The World Changes|Virginia 'Ginny' Clafflin Nordholm||-|The Kennel Murder Case|Hilda Lake||-|Jennie Gerhardt|Letty Pace||-|The Little Giant|Ruth Wayburn||-|rowspan="6"|1934|I Am a Thief|Odette Mauclair||-|The Case of the Howling Dog|Bessie Foley||-|The Man with Two Faces|Jessica Wells||-|Return of the Terror|Olga Morgan||-|Upper World|Mrs. Hettie Stream||-|Easy to Love|Charlotte Hopkins||-|rowspan="6"|1935|Man of Iron|Vida||-|Red Hot Tires|Patricia Sanford||-|Page Miss Glory|Gladys Russell||-|Dinky|Mrs. Martha Daniels||-|Straight from the Heart|Marian Henshaw||-|Lady from Nowhere|Polly||-|rowspan="4"|1936|Dodsworth|Mrs. Edith Cortright||-|Trapped by Television|Barbara 'Bobby' Blake||-|And So They Were Married|Edith Farnham||-|The Murder of Dr. Harrigan|Lillian Cooper||-|rowspan="2"|1937|The Hurricane|Madame Germaine De Laage||-|The Prisoner of Zenda|Antoinette de Mauban||-|rowspan="5"|1938|Listen, Darling|Mrs. Dorothy 'Dottie' Wingate||-|Woman Against Woman|Cynthia Holland||-|There's Always a Woman|Lola Fraser||-|Paradise for Three|Mrs. Irene Mallebre||-|No Time to Marry|Kay McGowan||-|1939|Midnight|Helene Flammarion||-|rowspan="2"|1940|Brigham Young|Mary Ann Young||-|Turnabout|Marion Manning||-|rowspan="2"|1941|The Maltese Falcon|Brigid O'Shaughnessy||-|The Great Lie|Sandra Kovak|Academy Award for Best Supporting Actress|-|rowspan="2"|1942|The Palm Beach Story|The Princess Centimillia||-|Across the Pacific|Alberta Marlow||-|rowspan="2"|1943|Thousands Cheer|Hyllary Jones||-|Young Ideas|Josephine 'Jo' Evans||-|rowspan="2"|1944|Blonde Fever|Delilah Donay||-|Meet Me in St. Louis|Mrs. Anna Smith||-|1946|Claudia and David|Elizabeth Van Doren||-|rowspan="4"|1947|Cass Timberlane|Queenie Havock||-|Cynthia|Louise Bishop||-|Desert Fury|Fritzi Haller||-|Fiesta|Señora Morales||-|1948|Act of Violence|Pat||-|rowspan="2"|1949|Any Number Can Play|Ada||-|Little Women|Marmee||-|rowspan="2"|1956|The Power and the Prize|Mrs. George Salt||-|A Kiss Before Dying|Mrs. Corliss||-|1957|The Devil's Hairpin|Mrs. Jargin||-|1958|This Happy Feeling|Mrs. Tremaine||-|1959|A Stranger in My Arms|Virgily Beasley||-|1961|Return to Peyton Place|Mrs. Roberta Carter||-|rowspan="2"|1964|Youngblood Hawke|Irene Perry||-|Hush... Hush, Sweet Charlotte|Mrs. Jewel Mayhew||}