His clear style and lack of sentimentality have kept him popular when many of his contemporaries have become obscure. His dark, sardonic views and vehemence as a critic, earned him the nickname "Bitter Bierce". Such was Bierce's venerable reputation, that it was feared that his judgment on any contemporary fiction of the day could "make or break" a writer's career.

Early life and military career
Born in a rural area of Meigs County, Ohio, Bierce resided during his adolescence in the town of Elkhart, Indiana. At the outset of the American Civil War, Bierce enlisted in the Ninth Regiment, Indiana Volunteers, as part of the Union Army. In February 1862, he was commissioned as a first lieutenant and served on the staff of Gen. William Babcock Hazen as a topographical engineer, making maps of likely battlefields. He fought bravely in several of the war's most important battles, at one point receiving newspaper attention for his daring rescue under fire of a gravely wounded comrade at the battle of Girard Hill, West Virginia. In June, 1864, he received a serious head wound at the Battle of Kennesaw Mountain and spent the rest of the summer on furlough, but returned to active duty in September, and was ultimately discharged from the army in January 1865.

His military career, however, resumed when, in the summer of 1866, he rejoined Gen. Hazen as part of the latter's expedition to inspect military outposts across the Western plains. The expedition proceeded by horseback and wagon from Omaha, Nebraska, arriving in San Francisco near the end of the year.

Journalism
In San Francisco, Bierce resigned from the Army and received the rank of brevet Major. He remained there for many years, eventually becoming famous as a contributor and/or editor for a number of local newspapers and periodicals, including The San Francisco News Letter, The Argonaut, and The Wasp. Bierce lived and wrote in England from 1872 to 1875. Returning to the United States, he again took up residence in San Francisco. In 1879–1880, he went to Rockerville and Deadwood, South Dakota, in the Dakota Territory, to try his hand as local manager for a New York mining company, but when the company failed he returned to San Francisco and resumed his career in journalism.

In 1887, he became one of the first regular columnists and editorialists to be employed on William Randolph Hearst's newspaper, the San Francisco Examiner, eventually becoming one of the most prominent and influential among the writers and journalists of the West Coast. In December 1899, he moved to Washington, D.C., but continued his association with the Hearst newspapers until 1906.

The McKinley accusation
Because of his penchant for biting social criticism and satire, Bierce's long newspaper career was often steeped in controversy. On several occasions his columns stirred up a storm of hostile reaction which created difficulties for Hearst. One of the most notable of these incidents occurred following the assassination of President William McKinley when Hearst's political opponents turned a satirical poem Bierce had written in 1900 into a cause célèbre. Bierce meant his poem, written on the occasion of the assassination of Governor-elect William Goebel of Kentucky, to express a national mood of dismay and fear, but after McKinley was shot in 1901 it seemed to foreshadow the crime:

The bullet that pierced Goebel's breast
Can not be found in all the West;
Good reason, it is speeding here
To stretch McKinley on his bier.

Hearst was (presumably) falsely accused by rival newspapers—and by then Secretary of State Elihu Root—of having called for McKinley's assassination. Despite a national uproar that ended his ambitions for the presidency (and even his membership in the Bohemian Club), Hearst neither revealed Bierce as the author of the poem, nor fired him.

Literary works
His short stories are considered among the best of the 19th century. He wrote realistically of the terrible things he had seen in the war in such stories as "An Occurrence at Owl Creek Bridge", "Killed at Resaca", and "Chickamauga".

Bierce was reckoned a master of "pure" English by his contemporaries, and virtually everything that came from his pen was notable for its judicious wording and economy of style. He wrote skillfully in a variety of literary genres, and in addition to his celebrated ghost and war stories he published several volumes of poetry and verse. His Fantastic Fables anticipated the ironic style of grotesquerie that turned into a genre in the 20th century.

One of Bierce's most famous works is his much-quoted book, The Devil's Dictionary, originally a newspaper serialization which was first published in book form in 1906 as The Cynic's Word Book. It offers an interesting reinterpretation of the English language in which cant and political double-talk are neatly lampooned.

Bierce's twelve-volume Collected Works were published in 1909, the seventh volume of which consists solely of "The Devil's Dictionary," the title Bierce himself preferred to "The Cynic's Word Book."

Disappearance
In October 1913, the septuagenarian Bierce departed Washington on a tour to revisit his old Civil War battlefields. By December, he had proceeded on through Louisiana and Texas, crossing by way of El Paso into Mexico, which was then in the throes of revolution. In Ciudad Juárez, he joined the army of Pancho Villa as an observer, in which role he participated in the battle of Tierra Blanca.

He is known to have accompanied Villa's army as far as the city of Chihuahua, Chihuahua. After a last letter to a close friend, sent from that city on December 26, 1913, he vanished without a trace, becoming one of the most famous disappearances in American literary history. Subsequent investigations to ascertain his fate were fruitless and, despite many decades of speculation, his disappearance remains a mystery.

In one of his last letters, Bierce wrote:

“Good-by — if you hear of my being stood up against a Mexican stone wall and shot to rags please know that I think that a pretty good way to depart this life. It beats old age, disease, or falling down the cellar stairs. To be a Gringo in Mexico — ah, that is euthanasia.”

Bierce in popular culture
Robert W. Chambers borrowed several terms and fictional locations (including, for instance, Carcosa and Hastur) from Bierce, for use in his book of horror short stories, The King in Yellow. The horror writer H.P. Lovecraft later incorporated these into his own work, as did other authors who later extended Lovecraft's characters and themes, collectively creating the Cthulhu Mythos.

Robert Bloch's short story "I Like Blondes" (published in Playboy, 1956) is constructed around a group of alien bodysnatchers frequenting Earth. The narrator's host body's "name was Beers...Ambrose Beers, I believe. He picked it up in Mexico a long time ago."

At least three films have been made of Bierce's story An Occurrence at Owl Creek Bridge. A silent movie version was made in the 1920s. A French version called La Rivière du Hibou, directed by Robert Enrico, was released in 1962 (available as of 2005). This is a black and white film, faithfully recounting the original narrative using voice-over. Another version, directed by Brian James Egan, was released in 2005. The 1962 film was also used for an episode of the television series The Twilight Zone: An Occurrence at Owl Creek Bridge. A copy of An Occurrence at Owl Creek Bridge appeared in the ABC television series Lost (ep. "The Long Con" - airdate February 8, 2006).

Mexican novelist Carlos Fuentes wrote Gringo Viejo (The Old Gringo), a fictionalized account of Bierce's disappearance. Fuentes's keenly observed novel was later adapted as a motion picture, with Gregory Peck in the title role.

Bierce appears as a character in the 2000 movie From Dusk Till Dawn 3: The Hangman's Daughter (set in 1913, a prequel to the original From Dusk Till Dawn). While traveling to join up with Villa, Bierce is first attacked by bandits, and then trapped in a bar filled with vampires bent on killing all the humans inside. This clearly fictional adventure also portrayed Bierce as an alcoholic. In that movie Ambrose Bierce was played by Michael Parks.

Bierce appears as a character in Robert A. Heinlein's novella Lost Legacy, (published in the short story collection Assignment in Eternity). In the story, Bierce is one of a league of humans who have learned to use the unused portions of their brains and have advanced mental powers.

Bierce appears as the main character and narrator in the story The Oxoxoco Bottle by Gerald Kersh. The bulk of the story purports to be a manuscript written by Bierce on his last journey in Mexico, and relates a very strange adventure. The manner of his death, however, remains a mystery at the end.

Bierce is depicted as a detective in series of mystery novels by Oakley Hall, including Ambrose Bierce and the Queen of Spades and Ambrose Bierce and the Death of Kings.

In DC Comics's miniseries Stanley and His Monster, Bierce (or at least a character claiming to be Bierce) appears as a sardonic trenchcoat-clad adventurer into the supernatual, very similar to John Constantine; although Bierce derides Constantine as a "clown," he admits that he and Constantine are but two of several trenchcoated occult adventurers at large in the world, perhaps an implication by the writer that the archetype of the sarcastic commentator on the occult, exemplified by Constantine, can be traced back to Bierce as narrator of his own horror stories. When the comic book Bierce learns that the boy Stanley's friend, the nameless Monster, is a demon, he considers vanquishing him but soon realizes that the Monster is a benevolent demon and instead helps Stanley and his friend against other demons.