LOS ANGELES — AT&T on Monday chose a Hollywood outsider, Ann Sarnoff, to run its recently acquired Warner Bros. movie and television studio, which will play a major role in the conglomerate’s coming streaming service.

Ms. Sarnoff, a New Yorker whose career has included leadership roles at Nickelodeon, the Women’s National Basketball Association, Dow Jones and BBC America, will take over as chief executive at Warner Bros. later this summer. Ms. Sarnoff has no film experience, which AT&T may see as an asset: She will not be beholden to entrenched Hollywood practices at a time when the entertainment business is rapidly moving online.

Her new boss, John Stankey, the chief executive of AT&T’s WarnerMedia division, said in a statement that Ms. Sarnoff brought a “proven track record of innovation, creativity and business results.”

In a phone interview, Ms. Sarnoff emphasized her ability to innovate and develop growth strategies. “It’s figuring out the potential of brands and properties and super-serving customers,” she said. “It’s looking at more marketing routes.”