For Michael Curtiz’s “Casablanca” (1942), Mr. Gold’s second assignment, he drew Humphrey Bogart in trench coat and fedora, dominant in the foreground, with a constellation of co-stars — Ingrid Bergman, Paul Henreid and others — in the airport fog behind him. To raise the drama, Mr. Gold put a pistol in Mr. Bogart’s hand. And he put fear and regret, not love, in Ms. Bergman’s eyes, to avoid stepping on his last lines.

“What I’ve got to do, you can’t be any part of,” Mr. Bogart’s Rick says as Ms. Bergman’s Ilsa sobs and the brutal airplane engines whine on the tarmac. “I’m no good at being noble, but it doesn’t take much to see that the problems of three little people don’t amount to a hill of beans in this crazy world. Someday you’ll understand that.”

The poster, like the film, came to embody an age of wartime sacrifice.

“Classic movie posters are memorable; they are held in as much affection as the movies themselves,” Lars Trodson wrote on the film website The Roundtable in 2009. “When a classic movie is matched by a classic poster, you’re held in the thrall of a distinct and pleasurable memory. The poster image becomes part of the movie experience, and is, in the end, another of the reasons why movies are so essential to us.”

Mr. Gold caught the steamy languor of Elia Kazan’s “A Streetcar Named Desire” (1951), with portraits of Marlon Brando’s crudely menacing Stanley Kowalski and Vivien Leigh’s birdlike Blanche Dubois thrown together in the mad cacophony of a dilapidated New Orleans tenement at the end of the Desire line.

For Ridley Scott’s terrifying 1979 interplanetary space thriller, “Alien,” Mr. Gold skipped the slathering title monster for something less obvious and more foreboding: a single large, dark egg, cracked and oozing a molten yellow light, hovering out in the galactic night.

And for Mr. Eastwood’s “Mystic River” (2003), a dark tragedy of child molestation and murder linking three men, friends since childhood in Irish Catholic Boston, who are haunted by secrets of grief and vengeance, Mr. Gold pared complexities to a penetrating simplicity. He depicted upside-down reflections of the three enigmatic men walking on water. “We bury our sins,” the caption says. “We wash them clean.”

Mr. Gold worked with many leading directors, including Vincente Minnelli, John Ford and John Huston. But his longest collaboration was with Mr. Eastwood.

It began in 1971 with “Dirty Harry,” the first of a series about a police detective whose gun, in the artist’s perspective, was bigger than he was. The poster placed Harry and the gun behind shattered glass, with the caption “Detective Harry Callahan. He doesn’t break murder cases. He smashes them.”

The Gold-Eastwood collaboration lasted four decades, with more than 30 posters for films that Mr. Eastwood produced, directed or starred in. Many used photographs or computer-generated images as poster art turned increasingly to technology.

Mr. Gold’s poster for the killing-and-revenge western “Unforgiven” (1992), often called his most compelling Eastwood portrait, was a computerized composite. It showed the back of the antihero, William Munny, in shadows, clad in a long coat, his head turned left for a partial profile of a man waiting to kill or be killed. Behind him, he grasps an astonishingly long-barreled revolver. There are no words.

“I don’t know what it is that first causes a person to become interested in a film — whether it’s the cast, or whether it’s the title, or whether it’s that first image,” Mr. Eastwood said in presenting The Hollywood Reporter’s lifetime achievement award to Mr. Gold in 1994. “I believe it is a combination of all of these. That’s the creative part of poster work — that image and what it does and how it affects an audience.”

William Gold, who always went by Bill, was born in Brooklyn on Jan. 3, 1921, the middle of three sons of Paul and Rose (Sachs) Gold. His father sold insurance. Bill and his brothers, Charles and Howard, attended public schools.

Bill loved to draw and copied illustrations from magazines. At Samuel J. Tilden High School, from which he graduated in 1939, he won art prizes and a scholarship to Pratt Institute, where he studied advertising and illustration and earned a certificate in advertising design in 1940

Mr. Gold married Pearl Tamases in 1941. The couple had two children and later divorced. In 1989 he married Susan Cornfield. Besides her, Mr. Gold is survived by his children, Robert and Marcy Gold, and two grandchildren.

In 1942, when New York was still a movie town with studios and front offices, he joined the Warner Bros. art department in Manhattan. His first assignment was a poster for “Yankee Doodle Dandy,” a tribute to the Broadway song and dance man George M. Cohan. He drew the star, Jimmy Cagney, saluting under a stars-and-stripes top hat and American flags, with stars shimmering like fireworks.

After his next poster, for “Casablanca,” Mr. Gold was drafted into the Army. He produced training films for World War II aircraft maintenance. Discharged in 1946, he resumed poster work for Warner Bros. and in 1947 was named art director. In the ’50s he made posters for “Strangers on a Train,” “Dial M for Murder,” “East of Eden,” “Giant” and many other films.

In the early ’60s, after Warner Bros. closed its New York advertising unit, he founded Bill Gold Advertising, with the studio as a principal client.

Mr. Gold often collaborated with illustrators on posters for which credit, if assigned at all, was blurred. One of his stars, Bob Peak, drew the poster for George Cukor’s “My Fair Lady,” (1964), but Mr. Gold took credit for the overall concept: a pink montage of turn-of-the-century London, with Rex Harrison as Henry Higgins and Audrey Hepburn as Eliza Doolittle under her picture hat and frilly umbrella.

The walls of Mr. Gold’s home in Old Greenwich, Conn., were lined with his posters for films including “Bonnie and Clyde” (1967), “A Clockwork Orange” (1971), “The Exorcist” (1973), “The Sting” (1973), “Platoon” (1986) and “The Untouchables” (1987). He retired in 2003 but continued to design posters. His last, in 2011, was for “J. Edgar,” Mr. Eastwood’s biopic of the longtime F.B.I. director, using Leonardo DiCaprio’s angry face for a likeness.