Sam "Ace" Rothstein is a fictional character from the 1995 film Casino, directed by Martin Scorsese. He is portrayed by actor Robert De Niro and is based on the real-life figure Frank "Lefty" Rosenthal. Ace is a skilled sports handicapper and casino manager in Las Vegas during the 1970s and 1980s, known for his expertise in gambling and casino operations. In the film, Ace's rise to power is marked by his ability to run a successful casino while navigating the complexities of organized crime. His relationships with characters like Ginger McKenna, played by Sharon Stone, and his partnership with Nicky Santoro, portrayed by Joe Pesci, highlight the challenges he faces in maintaining control over his empire amidst betrayal and violence.