William DeWolf Hopper, Jr., was born January 26, 1915, in New York City. He was the only child of noted actor, singer, comedian and theatrical producer DeWolf Hopper and his fifth wife, actress Hedda Hopper. William Hopper had one older half-brother, John A. Hopper, from his father’s second marriage in the 1880s. Hopper made his film debut as a baby in his father’s 1916 silent movie Sunshine Dad. His mother divorced his father in 1922 and moved to Hollywood with their son. Hedda Hopper became one of America’s best-known gossip columnists, with nearly 30 million readers in newspapers nationwide. Hopper began his acting career as a teenager. He made his first stage appearance at the Pasadena Community Playhouse, in She Loves Me Not. He worked in summer stock in Ogunquit, Maine. He appeared on Broadway in the short-lived comedy Order Please (1934)[8] and as a member of the ensemble in Katharine Cornell’s production of Romeo and Juliet (1934–35). In March 1936 Hopper — then working under the name Wolfe Hopper — won a contract at Paramount Pictures. Early in his film career, Hopper appeared in numerous movies, uncredited and also under the name DeWolf Hopper. In 1936, he played a small role as a soldier in the Columbia Pictures film The King Steps Out starring Grace Moore. In 1937 he portrayed the leading man in two films, Public Wedding with Jane Wyman and Over the Goal with June Travis. He also enjoyed significant roles alongside Ann Sheridan in The Footloose Heiress (1937) and Mystery House (1938). After that he had roles that included playing a sergeant in the John Ford Western, Stagecoach (1939); an intern in The Return of Dr. X (1939); a college football player in Over the Goal (1939); and reporters in Knute Rockne, All American (1940), The Maltese Falcon (1941) and Yankee Doodle Dandy (1942). Hopper became an actor because his mother expected it of him. “When I worked at Warner Bros.,” Hopper said, “I was so scared I stuttered all the time.”

In 1953 director William Wellman persuaded Hopper to resume his movie career with his 1954 film, The High and the Mighty, opposite Jan Sterling. Before filming began Hopper challenged Wellman because he suspected his mother had arranged the offer. “When it appeared Wellman was serious, I asked him if he knew whose son I was. He ignored me,” Hopper recalled. “I was so lousy, so nervous, I didn’t even know where the camera was. But somehow Billy got me through. Afterward, I thanked him. He said, ‘Thank me, my foot. After this, you’re going to be in every picture I make.’ I didn’t believe him.” Hopper subsequently appeared two of Wellman’s films, Track of the Cat (1954) and Good-bye, My Lady (1956). Hopper was cast to star opposite Claire Trevor in the live television drama, “No Sad Songs for Me”, broadcast April 14, 1955, on NBC’s Lux Video Theatre. He had such stage fright he initially cancelled: “I swore I’d never act again as long as I lived,” Hopper recalled. “Then I thought, what the heck, they can’t shoot me, and walked on the set. Something happened then. It was as if someone had surgically removed the nerves.” At last comfortable on screen, Hopper played the father of Natalie Wood in the James Dean classic, Rebel Without a Cause (1955), and the often absent father in The Bad Seed (1956). With Joan Taylor and a very young Bart Braverman, he starred in the classic Ray Harryhausen science-fiction film 20 Million Miles to Earth (1957). Also in 1957 he played a supporting role in the pilot episode of the television series The Restless Gun, which was broadcast as an episode of Schlitz Playhouse of Stars. His television guest appearances included the The Joseph Cotten Show, Gunsmoke, Fury, Studio 57 and The Millionaire.

In 1940 Hopper married actress Jane Kies, sister of Margaret Lindsay, whose professional name was Jane Gilbert. They had worked together on the 1939 film, Invisible Stripes. They had one daughter, Joan, born in 1947. On February 1, 1966, Hopper announced the death of his mother, actress and celebrated Hollywood columnist Hedda Hopper, from double pneumonia. Despite rumors to the contrary, actor Dennis Hopper was not related to William Hopper. Hopper entered Desert Hospital in Palm Springs, California, on February 14, 1970, after suffering a stroke. He died of pneumonia three weeks later, on March 6, at age 55. He was buried in Rose Hills Memorial Park in Whittier, California.