The Game of Thrones star has become a brand ambassador for feminine hygiene product company Always and she helped the company unveil its new #likeagirl advert in New York City this week (beg06Jul15).

During the launch of the film, which aims to highlight how many women feel limited by society's expectations of them, Williams, 18, urged fellow young females to aim high.

She said, "It's time for girls to be free; free to nurture and celebrate whatever qualities and talents make them different. It's the most liberating time moving into adulthood. But that transition should not happen with labels and expectations, but with an open heart and mind... Confidence gives us what we need in life. So build yours, protect yours, fight for yours, grab it with both hands and hold it like the course of your future depends on it. Because it does... The world is desperate for leaders, male and female. It's not about gender, it's about purpose... The Like a Girl movement has done so much to elevate the conversation. Girls, we have to stick together, please support each other... You're allowed to be the most important person in your story."

Williams follows in the footsteps of fellow British actress Emma Watson who unveiled a pro-feminism campaign for the United Nations last year (14).