Loy was born Myrna Adele Williams in Radersburg, Montana (near Helena), the daughter of Adelle Mae (née Johnson) and rancher David Franklin Williams. She was of Welsh and Scottish ancestry. Loy's first name came from a train station whose name her father liked. Her father was also a banker and real estate developer and the youngest man ever elected to the Montana state legislature. Her mother studied music at the American Conservatory of Music in Chicago.
Myrna Williams made her stage debut at age 12 in Helena's Marlow Theater in a dance she choreographed based on "The Blue Bird" from the Rose Dream Operetta. She moved to the Palms district of Los Angeles, California when she was 13, after her father's death. She attended the Westlake School for Girls in Los Angeles's Holmby Hills neighborhood. At 15, she began appearing in local stage productions. She went to Venice High School in Venice, California.
In 1921, she posed for Harry Winebrenner's statue titled "Spiritual," which remained in front of Venice High School throughout the 20th century and can be seen in the opening scenes of the film Grease (1978). The statue was removed from where it stood after vandalism and neglect had destroyed it. A group of alumni are raising money to re-create the statue, and their goal is to have it ready to unveil in spring 2009.
Myrna Loy in one of her early film roles, in the 1926 film Across the PacificNatacha Rambova, the second wife of Rudolph Valentino, arranged a screen test for Loy, which she failed. She kept auditioning and in 1925, appeared in the Rambova-penned movie What Price Beauty?, opposite Nita Naldi. Her silent film roles were mainly those of vampish exotic women. For a few years, she struggled to overcome this stereotype with many producers and directors believing that, while she was perfect as a femme fatale, she was capable of little more. Studios thought she was perfect for Asian roles and cast her in yellowface several times. She starred in Thirteen Women (1932), playing a villainous Eurasian half-breed.
Her breakthrough occurred with the advent of talkies: she appeared in 1927's The Jazz Singer as an uncredited chorus girl. In 1929, she improvised a "foreign" accent, and sang and danced in Warner Brothers' first musical The Desert Song (1929). Loy later commented on the film's success and noted "...it kind of solidified my exotic non-American image". She was quickly cast in a number of early lavish Technicolor musicals including The Show of Shows (1929), The Bride of the Regiment (1930) and Under A Texas Moon (1930). Loy became associated with musicals and when they went out of favor with the public, late in 1930, her career went into a slump.
In 1934, she appeared in Manhattan Melodrama with Clark Gable and William Powell. When the gangster John Dillinger was shot to death after leaving a screening of the film, it received widespread publicity, with some newspapers reporting that Loy had been Dillinger's favorite actress. Loy later expressed distaste for the manner in which the film studio had exploited Dillinger's death.
 Rise to stardom
After appearing with Ramón Novarro in The Barbarian (1933), Loy landed the part that established her as a major actress, Nora Charles in The Thin Man (1934). Director W. S. Van Dyke chose Loy after he detected a wit and sense of humor that her previous films had not revealed. At a Hollywood party, he pushed her into a swimming pool to test her reaction, and felt that her aplomb in handling the situation was exactly what he envisioned for Nora. Louis B. Mayer at first refused to allow Loy to play the part, saying that she was a dramatic actress only, but Van Dyke insisted. Mayer relented on the condition that filming be completed within three weeks, as Loy was committed to start filming Stamboul Quest (1934). The Thin Man became one of the year's biggest hits, and was nominated for an Academy Award for Best Picture. Loy received excellent reviews and was acclaimed for her comedic skills. She and her costar William Powell proved to be a popular screen couple and appeared in 14 films together, the most prolific pairing in Hollywood history. Loy later referred to The Thin Man as the film "that finally made me... after more than 80 films".
Nora and Nick Charles: William Powell and Loy in the 1936 film After the Thin ManHer successes in Manhattan Melodrama and The Thin Man marked a turning point in her career and she was cast in more important pictures. Such films as Wife vs. Secretary (1936) with Clark Gable and Jean Harlow and Petticoat Fever (1936) with Robert Montgomery gave her opportunity to develop comedic skills. She made four films in close succession with William Powell: Libeled Lady (1936), which also starred Spencer Tracy and Jean Harlow, The Great Ziegfeld (1936), in which she played Billie Burke opposite Powell's Florenz Ziegfeld, the second "Thin Man" film, After the Thin Man, and the romantic comedy Double Wedding (1937). She also made three more films with Clark Gable. Parnell was an historical drama and one of the most poorly received films of either Loy's or Gable's career, but their other pairings in Test Pilot and Too Hot to Handle (both 1938) were successes.
During this period, Loy was one of Hollywood's busiest and highest paid actresses, and in 1937 and 1938 she was listed in the annual "Quigley Poll of the Top Ten Money Making Stars", which was compiled from the votes of movie exhibitors throughout the U.S. for the stars that had generated the most revenue in their theaters over the previous year.
By this time Loy was highly regarded for her performances in romantic comedies and she was anxious to demonstrate her dramatic ability, and was cast in the lead female role in The Rains Came (1939) opposite Tyrone Power. She filmed Third Finger, Left Hand (1940) with Melvyn Douglas and appeared in I Love You Again (1940), Love Crazy (1941) and Shadow of the Thin Man (1941), all with William Powell.
With the outbreak of World War II, she all but abandoned her acting career to focus on the war effort and worked closely with the Red Cross. She was so fiercely outspoken against Adolf Hitler that her name appeared on his blacklist. She helped run a Naval Auxiliary Canteen and toured frequently to raise funds.
Loy in The Best Years of Our Lives
 Later career
She returned to films with The Best Years of Our Lives (1946), playing the wife of returning serviceman Fredric March. In later years, Loy considered this film her proudest acting achievement. Throughout her career, she had championed the rights of black actors and characters to be depicted with dignity on film.
Loy was paired with Cary Grant in David O. Selznick's comedy film The Bachelor and the Bobby-Soxer (1947). The film co-starred a teenage Shirley Temple. Following its success she appeared again with Grant in Mr. Blandings Builds His Dream House (1948), and with Clifton Webb in Cheaper by the Dozen (1950).
Her film career continued sporadically afterwards. In 1960, she appeared in Midnight Lace and From the Terrace, but was not in another until 1969 in The April Fools. She also returned to the stage, making her Broadway debut in a short-lived 1973 revival of Clare Boothe Luce's The Women.
 Personal life
Loy was married and divorced four times:
1936-1942 Arthur Hornblow, Jr., producer
1942-1944 John Hertz Jr. of the Hertz Rent A Car family
1946-1950 Gene Markey, producer and screenwriter
1951-1960 Howland H. Sergeant, UNESCO delegate
Loy had no children of her own, though it is documented that she was very close to the children of her first husband, Arthur Hornblow. "Some perfect wife I am," she said, referring to her typecasting. "I've been married four times, divorced four times, have no children, and can't boil an egg."
In later life, she assumed a more influential role as Co-Chairman of the Advisory Council of the National Committee Against Discrimination in Housing. In 1948 she became a member of the U.S. National Commission for UNESCO, the first Hollywood celebrity to do so. She was also an active Democrat.
Her autobiography, Myrna Loy: Being and Becoming, was published in 1987. Loy had a mastectomy in both 1975 and 1979, but survived breast cancer then..
On December 14, 1993, she died during surgery in New York City at the age of 88. She was cremated in New York and the ashes interred at Forestvale Cemetery, in Helena, Montana.
Myrna Loy's grave in Forestvale Cemetery, Helena, MT
In 1965 she won the Sarah Siddons Award for her work in Chicago theatre. She also received a Lifetime Achievement Award from the Kennedy Center in 1988.
Although Loy was never nominated for an Academy Award for any single performance, after an extensive letter writing campaign and years of lobbying by screenwriter and then-Writers Guild of America, west board member Michael Russnow, who enlisted the support of Loy's former screen colleagues and friends such as Roddy McDowall, Sidney Sheldon, Harold Russell and many others, she received an Academy Honorary Award in 1991, "for her career achievement". She accepted via camera from her New York home, making only a short acceptance speech of, "You've made me very happy. Thank you very much." It was her last public appearance in any medium.
Myrna Loy has a star on the Hollywood Walk of Fame at 6685 Hollywood Boulevard. A building at Sony Pictures Studios, formerly MGM Studios, in Culver City is named in her honor.
In 1991, The Myrna Loy Center for the Performing and Media Arts opened in downtown Helena, Montana, Loy's hometown. Located in the historic Lewis and Clark County Jail, it sponsors live performances and alternative films for under-served audiences.