Robert M. Peak was an American commercial illustrator. He is best known for his developments in the design of the modern film poster.

His artwork has been on the cover of Time magazine, TV Guide, and Sports Illustrated. He also illustrated advertisements and U.S. postage stamps.

Bob Peak was born in Denver, Colorado and grew up in Wichita, Kansas. He knew from an early age that he wanted to be a commercial illustrator. He majored in geology at the University of Wichita (nka Wichita State University) and got a part-time job in the art department of McCormick-Armstrong. After serving in the military during the Korean War, Peak transferred to the Art Center College of Design in Los Angeles, California, graduating in 1951.

In 1953, Peak moved to New York City and landed an Old Hickory Whiskey advertising campaign. His work went on to appear in major advertising and national magazines.

He was the father of Matthew Peak, who is best known for his film posters for the Nightmare On Elm Street films.

United Artists studio hired Peak in 1961 to design the poster images for the film West Side Story. The success of Peak's work on that film led to work on posters for designer Bill Gold, including the big-budget musicals My Fair Lady and Camelot. In the mid-1970s Peak's style would become familiar to fans of science fiction films when he created the poster art for the futuristic film Rollerball (1975), which was followed by the first six Star Trek films, Superman (1978), Excalibur (1981), both Derek Flint films, Apocalypse Now (1979), The Spy Who Loved Me and other James Bond concepts. By the 1980s only the film poster artist Drew Struzan was in as much demand by film directors.

Peak received a commission from the U.S. Postal Service to design 30 stamps for the 1984 Summer Olympics in Los Angeles and the 1984 Winter Olympics in Sarajevo, Yugoslavia.

From January 20 through April 17, 2011, the Academy of Motion Picture Arts and Sciences presented the "Bob Peak: Creating the Modern Movie Poster" exhibit at its headquarters building in Beverly Hills.

Peak taught in his own college and later at Art Students League of New York, Pratt Institute and Famous Artists School.

Depicting the memorable scene in Francis Ford Coppola's film where Col. Kurtz, played by Marlon Brando, confronts Capt. Benjamin L. Willard, played by Martin Sheen, Peak's haunting illustration shows Brando's clenched fist squeezing a wet rag over his bald head, with water dripping from his forehead downwards off his pale, gaunt face. On October 4, 2021, this poster sold for $212,500, a world record for this artist.

In 1961, Peak was named Artist of the Year by the Graphic Artists Guild New York chapter. He won eight Awards of Excellence and four gold medals from Society of Illustrators. In 1977, the Society of Illustrators inducted him to its Hall of Fame. The Hollywood Reporter presented him the 1992 Key Art Award, now known as the Clio Entertainment Awards.