Millar was born in Los Gatos, California and raised in his parents' native Kitchener, Ontario, Canada, where he started college. When his father abandoned his family unexpectedly, Macdonald lived with his mother and various relatives, moving several times by his sixteenth year. The prominence of broken homes and domestic problems in his fiction has its roots in his youth.

In Canada, he met and married Margaret Sturm in 1938. They had a daughter, Linda, who died in 1970. He began his career writing stories for pulp magazines. Macdonald attended the University of Michigan, where he earned a Phi Beta Kappa key and a Ph. D. in literature. While doing graduate study at the he completed his first novel, The Dark Tunnel, in 1944. At this time, he wrote under the name John Macdonald, in order to avoid confusion with his wife, who was achieving her own success writing as Margaret Millar. He then changed briefly to John Ross Macdonald before settling on Ross Macdonald, in order to avoid mixups with contemporary John D. MacDonald. After serving at sea as a naval communications officer from 1944 to 1946, he returned to Michigan, where he obtained his Ph.D. degree in 1951.

Macdonald's popular detective Lew Archer derives his name from one of the author's high school teachers (not from Sam Spade's partner Miles Archer) and from Lew Wallace, author of Ben-Hur: A Tale of the Christ. Macdonald first introduced the tough but humane private eye in the 1946 short story "Find the Woman." A full-length novel, The Moving Target, followed in 1949. This novel (the first in a series of eighteen) would become the basis for the 1966 Paul Newman film Harper.[1] In the early 1950s, he returned to California, settling for some thirty years in Santa Barbara, the area where most of his books were set. (Macdonald's fictional name for Santa Barbara was Santa Teresa; this "pseudonym" for the town was subsequently resurrected by Sue Grafton, whose "alphabet novels" are also set in Santa Teresa.) The very successful Lew Archer series, including bestsellers The Goodbye Look, The Underground Man, and Sleeping Beauty, concluded with The Blue Hammer in 1976. Macdonald died of Alzheimer's Disease.