Fraser was born to Scottish parents in Carlisle, England. His father was a doctor and his mother a nurse. It was his father who passed on to Fraser his love of reading, and a passion for his Scottish heritage.

Fraser was educated at Carlisle Grammar School and The Glasgow Academy, and Fraser later described himself as a poor student due to "sheer laziness". This meant that he was unable to follow his father's wishes and study medicine.

In 1943, during World War II, he enlisted in The Border Regiment. He was assigned to 9 Section, B Company, 9th Battalion (Bn) in the Indian 17th Infantry Division, known as the Black Cat Division for the flashes worn by the troops. Fraser was made a lance corporal four times, but was reduced to private three times for minor offences, one of them losing a tea urn. He finally kept the rank and held it until he went to the War Office Selection Board (WOSB) for a commission. He detailed his active service with the Border Regiment in his autobiographical book, Quartered Safe Out Here.

After completion of his OCTU (Officer Cadet Training Unit) course, Fraser was granted a commission into the Gordon Highlanders. He served with them in the Middle East and North Africa immediately after the war. Fraser decided against remaining with the army and took up his demobilisation. He has written semi-autobiographical stories and anecdotes of his time with the Gordon Highlanders in the so-called "McAuslan" series.

After his discharge, Fraser returned to the United Kingdom. He worked on the Carlisle Journal and married another journalist, Kathleen Hetherington. They travelled to Canada, working on newspapers there, before returning again to Scotland. Starting in 1953, he worked for many years as a journalist at the Glasgow Herald newspaper where he was deputy editor from 1964 until 1969. He briefly held the title of acting editor. Fraser resigned and gained fame as a novelist and a screen writer. He is best known for his Flashman series of historical novels, purportedly written by Harry Flashman, a fictional coward and bully originally created by Thomas Hughes in Tom Brown's School Days. The novels are presented as "packets" of memoirs written by the nonagenarian Flashman, who looks back on his days as a hero of the British Army during the 19th century. The series begins with Flashman, and is notable for the accuracy of the historical settings and praise from critics. P.G. Wodehouse said of Flashman, “If ever there was a time when I felt that ‘watcher-of-the-skies-when-a-new-planet’ stuff, it was when I read the first Flashman.”

George MacDonald Fraser was made an Officer of the Order of the British Empire (OBE) in 1999.

A traditionalist, he was an Honorary Member of the British Weights and Measures Association, which opposes compulsory conversion to the metric system.

He died on 2 January 2008 from cancer, aged 82.

He is the father of novelist Caro Fraser.

The Flashman series constitute Fraser's major works. There are 12 books in the series:

• Flashman (1969)
• Royal Flash (1970)
• Flash for Freedom! (1971)
• Flashman at the Charge (1973)
• Flashman in the Great Game (1975)
• Flashman's Lady (1977)
• Flashman and the Redskins (1982)
• Flashman and the Dragon (1985)
• Flashman and the Mountain of Light (1990)
• Flashman and the Angel of the Lord (1994)
• Flashman and the Tiger (1999)
• Flashman on the March (2005)

Fraser's other works include:

• Quartered Safe Out Here (1992), a memoir of his experiences as an infantryman in the Border Regiment during the Burma Campaign of World War II
• The "Dand MacNeill" or "McAuslan" stories, a semi-autobiographical series of short stories based on the author's experiences in the Gordon Highlanders in North Africa and Scotland soon after World War II. Some of the stories were originally by-lined "by Dand MacNeill", a play on the regimental motto BYDAND, meaning standfast:
• The General Danced at Dawn (1970)
• McAuslan in the Rough (1974)
• The Sheikh and the Dustbin (1988)
• The Complete McAuslan (HarperCollins 2000) (All the stories in the three volumes, with a new introduction.)
• The Steel Bonnets (1971), a history of the Border Reivers of the Anglo-Scottish Border.
• The Hollywood History of the World: From One Million Years B.C. to Apocalypse Now. (1988, revised 1996) The book discusses how Hollywood deals with history. It concludes that the standard of historical analysis in most movies is far better than one might imagine. The text is illustrated by comparative images of figures from history and the actors who portrayed them in film. In many cases the similarities are striking.
• The Pyrates (1983), a tongue-in-cheek novel incorporating all the possible buccaneer film plots into one.
• Black Ajax (1997), a novel about Tom Molineaux, a 19th century black prizefighter in England. (As in Mr American, this novel is also connected to the Flashman series - in this case Sir Harry Flashman's father plays a minor role.)
• Mr American (1980), a novel about a mysterious American in England, the book comes to life in the hero's dealings with the aged General Harry Flashman.
• The Candlemass Road (1993), a short novel about the Border Reivers of the 16th century.
• The Light's on at Signpost (2002), a memoir of the author's days writing in Hollywood, interspersed with intemperate rants against "political correctness" and New Labour.
• The Reavers (2007), a comic novel of the Border Reivers in the style of his earlier nove; 'The Pyrates'

Screenplays

Fraser wrote or co-wrote the screenplays for:

• The Three Musketeers (1973)
• The Four Musketeers (1974)
• Royal Flash (1975, adapted from his novel)
• Crossed Swords (US) or The Prince and the Pauper (UK) (1977)
• Force 10 From Navarone (uncredited) (1978)
• Octopussy (1983)
• Red Sonja (1985)
• The Return of the Musketeers (1989)
• An unproduced screenplay for The Lone Ranger, date unknown
• Some script-doctor work on Superman II

George Macdonald Fraser's Flashman at the Charge was in the April and June 1973 Playboy issues.