Jessurun James Oppenheimer (November 11, 1913 – December 27, 1988) was an American radio and television writer, producer, and director. He was the producer and head writer of the CBS sitcom I Love Lucy.

Lucille Ball called Oppenheimer “the brains” behind I Love Lucy. As series creator, producer, and head writer, “Jess was the creative force behind the ‘Lucy’ show,” according to I Love Lucy director William Asher. “He was the field general. Jess presided over all the meetings, and ran the whole show. He was very sharp.”

He was born into a secular Jewish family in San Francisco, where in the third grade he was chosen as a subject of Stanford University professor Lewis Terman's study of gifted children. Prof. Terman's assistant noted in Oppenheimer's file, "I could detect no signs of a sense of humor."

During his junior year at Stanford during the 1930s, Oppenheimer visited the studios of radio station KFRC in San Francisco, and soon started spending all his spare time there. He made his broadcast debut performing a comedy sketch he'd written on the station's popular coast-to-coast comedy-variety radio program, Blue Monday Jamboree.

In 1936, Oppenheimer moved to Hollywood, where in his first week he was hired as a comedy writer on Fred Astaire's radio program. When Astaire's show ended the following year, Oppenheimer landed a job as a radio gag writer for Jack Benny. He later wrote comedy for such other variety programs as The Chase and Sanborn Hour with Edgar Bergen and Charlie McCarthy," "The Lifebuoy Program starring Al Jolson," "The Gulf Screen Guild Show," and "The Rudy Vallee Program." As a staff writer on those programs, Oppenheimer wrote sketch comedy for many Hollywood stars, including Fanny Brice, George Burns and Gracie Allen, Bing Crosby, Marlene Dietrich, Judy Garland, Bob Hope, and Ginger Rogers.

With the start of World War II, Oppenheimer joined the United States Coast Guard and was posted to the Public Relations Department. The sailor at the next desk was a young agent named Ray Stark, the son-in-law of Fanny Brice. Stark immediately hired Oppenheimer to write for the popular radio program, The Baby Snooks Show, which starred Brice as a wise-beyond-her-years little girl who constantly drove her daddy crazy.

In 1948, shortly after The Baby Snooks Show went off the air, CBS asked Oppenheimer to write a script for a new unsponsored radio sitcom, My Favorite Husband, starring Lucille Ball. In the handful of episodes that had already aired, Ball had played "Liz Cugat," a "gay, sophisticated," socialite wife of a bank vice president.

Oppenheimer decided to make her radio character more like Baby Snooks: less sophisticated, more childlike, scheming, and impulsive—taking Lucy and the show in a new direction, with broad, slapstick comedy. The show was a huge success. CBS quickly signed Oppenheimer as the show's head writer, producer, and director. Oppenheimer was hesitant to accept the position after being warned by his friends against working with Ball, but he decided to accept anyway after seeing her brilliant performance of his script. Soon the series gained both a sponsor and a much larger audience. My Favorite Husband also marked the beginning of Oppenheimer's successful collaboration with future I Love Lucy writers Madelyn Pugh and Bob Carroll, Jr.