Frank Lawrence Rosenthal  also known as "Lefty" Rosenthal, was an American professional sports bettor, former Las Vegas casino executive, and organized crime associate. Rosenthal, who was once called "the greatest living expert on sports gambling" by Sports Illustrated, is credited with bringing increased exposure to sports betting to Las Vegas in the 1970s.

Rosenthal's life and career in Las Vegas served as the basis of Martin Scorsese's 1995 film Casino, where he was portrayed by Robert De Niro and re-named Sam "Ace" Rothstein.