J. Robert Bren, born José Roberto Bustamante Gutiérrez on July 23, 1903, in Guanajuato, Mexico, was a Mexican-American screenwriter and film producer active from the mid-1930s through the mid-1950s, credited with stories or screenplays for thirty feature films and producing at least two.

He began in the industry on the sound crew for the 1933 film Face in the Sky before transitioning to writing stories, starting with the 1934 20th Century Fox comedy Looking for Trouble starring Spencer Tracy and Jack Oakie, as well as co-authoring the story for The Band Plays On that same year with Byron Morgan.

In 1937, he collaborated on multiple projects, including expanding a Damon Runyon story into Racing Lady with Ann Dvorak and contributing to the screenplay for The Man Who Found Himself, Joan Fontaine's first starring role opposite John Beal.​

J. Robert Bren frequently partnered with Gladys Atwater, his wife and writing collaborator, on screenplays like Crime Ring and This Marriage Business in 1938, Five Little Peppers and How They Grew in 1939, and Parents on Trial that same year.

Their work extended to wartime stories such as In Old California in 1942 starring John Wayne, Underground Agent, and American Empire, while he produced and wrote First Yank into Tokyo in 1945, securing authentic footage of Japanese Prime Minister Kuniaki Koiso for its opening. He also produced El Paso in 1949 from their story and co-wrote The Great Sioux Uprising in 1953.​

Later credits included the story for Naked Alibi in 1954 starring Sterling Hayden and Gloria Grahame, Siege at Red River, Overland Pacific, and his final big-screen effort, The Treasure of Pancho Villa, co-written with Atwater and featuring Rory Calhoun, Shelley Winters, and Gilbert Roland.

Beyond films, he served on the California State Welfare Board in 1949 alongside advocate Hazel Hurst, inspiring a screenplay based on her life promoting guide dogs for the blind. He died on October 1, 1981, in Los Angeles at age 78.​