Ruben Samuel Fleischer (/ˈflaɪʃər/; born October 31, 1974) is an American film director, film producer, television producer, music video director, and commercial director living in Monclair, New Jersey. He is best known as the director of Zombieland (2009), his first feature film, and its sequel Zombieland: Double Tap (2019). He also directed 30 Minutes or Less, Gangster Squad, Uncharted, and Venom (2018), which features the same Marvel Comics character. Previously, he directed television commercials for brands such as Cisco, Eurostar, ESPN, and Burger King, as well as music videos for artists such as M.I.A., Electric Six, DJ Format, and Gold Chains.

Fleischer was born and raised in Washington, D.C., the son of Karen Lee (née Samuel) and David Elliot Fleischer, a doctor at the Mayo Clinic in Arizona and a professor of medicine. His brother Lucas works in new media. His father was born into a Jewish family, and his mother converted to Judaism. Fleischer was raised in Reform Judaism.

After majoring in history at Wesleyan University, Fleischer moved to San Francisco, where he worked as a freelance HTML programmer, not knowing what he wanted to do in life.

On the advice of a close friend, Mike White (also a Wesleyan University graduate), Fleischer got a job as an assistant in the writers' office of Dawson's Creek. He eventually turned to directing and worked his way up in the industry, directing music videos and television commercials before making his first feature film, Zombieland, in 2009. His second feature film, 30 Minutes or Less, was released on August 12, 2011.