Samuel Dashiell Hammett (May 27, 1894 – January 10, 1961) was an American author of hard-boiled detective novels and short stories. Among the enduring characters he created are Sam Spade (The Maltese Falcon), Nick and Nora Charles (The Thin Man), and the Continental Op (Red Harvest and The Dain Curse).

In addition to the significant influence his novels and stories had on film, Hammett "is now widely regarded as one of the finest mystery writers of all time" and was called, in his obituary in The New York Times, "the dean of the... 'hard-boiled' school of detective fiction". Time magazine included Hammett's 1929 novel Red Harvest on a list of the 100 best English language novels published between 1923 and 2005.

Hammett was born on a farm called Hopewell and Aim off Great Mills Road, St. Mary's County, in southern Maryland. His parents were Richard Thomas Hammett and Anne Bond Dashiell. (The Dashiells are an old Maryland family, the name being an Anglicization of the French De Chiel). He was baptized a Roman Catholic and grew up in Philadelphia and Baltimore. "Sam," as he was known before he began writing, left school when he was 13 years old and held several jobs before working for the Pinkerton National Detective Agency. He served as an operative for the Pinkertons from 1915 to February 1922, with time off to serve in World War I. However, the agency's role in union strike breaking eventually disillusioned him.

During the war, Hammett enlisted in the United States Army and served in the Motor Ambulance Corps. However, he became ill with the Spanish flu and later contracted tuberculosis. He spent the war as a patient in Cushman Hospital, Tacoma, Washington. While hospitalized he met a nurse, Josephine Dolan.

Hammett married Josephine Dolan and they had two daughters, Mary Jane (1921 - 10 - 15) and Josephine (1926). Shortly after the birth of their second child, Health Services nurses informed Josephine that due to Hammett's TB, she and the children should not live with him full time. So they rented a place in San Francisco. Hammett would visit on weekends, but the marriage soon fell apart. Hammett continued to support his wife and daughters financially with the income he made from his writing.

Hammett turned to drinking, advertising, and, eventually, writing. His work at the detective agency provided him the inspiration for his writings. Known for his authenticity and realism, Hammett drew on his experiences as a Pinkerton operative. As Hammett said: "All my characters were based on people I've known personally, or known about." Raymond Chandler, the writer often considered Hammett's successor, summarized his accomplishments:

"Hammett was the ace performer... He is said to have lacked heart; yet the story he himself thought the most of [The Glass Key] is the record of a man's devotion to a friend. He was spare, frugal, hard-boiled, but he did over and over again what only the best writers can ever do at all. He wrote scenes that seemed never to have been written before."

- Chandler, The Simple Art of Murder

From 1929 to 1930 Dashiell was romantically involved with Nell Martin, an author of short stories and several novels. He dedicated The Glass Key to her, and in turn, she dedicated her novel Lovers Should Marry to Hammett. In 1931, Hammett embarked on a 30 year affair with playwright Lillian Hellman. This relationship was portrayed in the film Julia, in which Hammett was portrayed by Jason Robards and Hellman by Jane Fonda, in Oscar winning and nominated performances respectively.

He wrote his final novel in 1934, and devoted much of the rest of his life to left wing activism. He was a strong anti-fascist throughout the 1930s and in 1937 he joined the American Communist Party. As a member of the League of American Writers, he served on its Keep America Out of War Committee in January 1940 during the period of the Hitler - Stalin pact.

In 1942, after Pearl Harbor, Hammett enlisted in the United States Army. Though he was a disabled veteran of World War I, and a victim of tuberculosis, he pulled strings in order to be admitted to the service. He spent most of World War II as an Army sergeant in the Aleutian Islands, where he edited an Army newspaper. He came out of the war suffering from emphysema. As a corporal in 1943, he co-authored The Battle of the Aleutians with Cpl. Robert Colodny under the direction of Infantry Intelligence Officer Major Henry W. Hall.

After the war, Hammett returned to political activism, "but he played that role with less fervor than before." He was elected President of the Civil Rights Congress of New York on June 5, 1946 at a meeting held at the Hotel Diplomat in New York City, and "devoted the largest portion of his working time to CRC activities." In 1946, a bail fund was created by the CRC "to be used at the discretion of three trustees to gain the release of defendants arrested for political reasons." Those three trustees were Hammett, who was chairman, Robert W. Dunn, and Frederick Vanderbilt Field, "millionaire Communist supporter." On April 3, 1947, the CRC was designated a Communist front group on the Attorney General's List of Subversive Organizations, as directed by U.S. President Harry S. Truman’s Executive Order 9835.

The CRC's bail fund gained national attention on November 4, 1949, when bail in the amount of "$260,000 in negotiable government bonds" was posted "to free eleven men appealing their convictions under the Smith Act for criminal conspiracy to teach and advocate the overthrow of the United States government by force and violence." On July 2, 1951, their appeals exhausted, four of the convicted men fled rather than surrender themselves to Federal agents and begin serving their sentences. At that time, the United States District Court for the Southern District of New York issued subpoenas to the trustees of the CRC bail fund in an attempt to learn the whereabouts of the fugitives. Hammett testified on July 9, 1951 in front of United States District Court Judge Sylvester Ryan, facing questioning by Irving Saypol, the United States Attorney for the Southern District of New York, described by Time as "the nation's number one legal hunter of top Communists". During the hearing Hammett refused to provide the information the government wanted, specifically, the list of contributors to the bail fund, "people who might be sympathetic enough to harbor the fugitives." Instead, on every question regarding the CRC or the bail fund, Hammett took the Fifth Amendment, refusing to even identify his signature or initials on CRC documents the government had subpoenaed. As soon as his testimony concluded, Hammett was immediately found guilty of contempt of court. Hammett served time in a West Virginia federal penitentiary where, according to Lillian Hellman, he was assigned to cleaning toilets.

During the 1950s he was investigated by Congress (see McCarthyism), and testified on March 26, 1953 before the House Un-American Activities Committee. Although he testified to his own activities, he refused to cooperate with the committee and was blacklisted.

A lifetime's heavy consumption of alcohol and cigarettes worsened Hammett's tuberculosis contracted in World War I, and then according to Hellman "jail had made a thin man thinner, a sick man sicker . . . I knew he would now always be sick." He may have meant to start a new literary life with the novel Tulip, but left it unfinished perhaps because he was "just too ill to care, too worn out to listen to plans or read contracts. The fact of breathing, just breathing, took up all the days and nights."

As the years of the 1950s wore on Hellman says Hammett became "a hermit," his decline evident in the clutter of his rented "ugly little country cottage" where "[t]he signs of sickness were all around: now the phonograph was unplayed, the typewriter untouched, the beloved foolish gadgets unopened in their packages." Hammett no longer could live alone and they both knew it, so the last four years of his life he spent with Hellman. "Not all of that time was easy, and some of it very bad, " she says but, "guessing death was not too far away, I would try for something to have afterwards." January 10, 1961, Hammett died in New York City's Lenox Hill Hospital, of lung cancer, diagnosed just two months before. As a veteran of two World Wars, he was buried at Arlington National Cemetery.

Fellow crime writer and former San Francisco detective Joe Gores wrote a novel in 1975 entitled Hammett, which imagines Hammett himself being drawn back to the work of a private eye in order to honor a debt to his mentor. The novel was adapted into the film Hammett (1982), which was produced by Francis Ford Coppola and directed by Wim Wenders. In the film, Frederic Forrest plays Hammett. Forrest also played Hammett in the TV film Citizen Cohn (1992).

Gores also recently wrote Spade & Archer (2009), a prequel to The Maltese Falcon. The novel investigates in richer detail the back stories of Sam Spade, his partner Miles Archer, and other characters from the original story. Gores was able to secure permission from Jo Marshall, Hammett's daughter, and Julie Rivett, Marshall's daughter and Hammett's granddaughter, to write the book. Although Marshall at first refused, the Hammett family later changed their mind because they felt that Gores was the right person to tell the story, primarily because he was a crime writer and a former San Francisco private investigator, just like Hammett. According to Rivett, "[Gores] walked the walk as well as he talked the talk. He knows as well as anyone where those characters came from."

In Laurie R. King's Locked Rooms, Hammett assists Sherlock Holmes and Mary Russell in solving a mystery from Russell's childhood.