LOS ANGELES — Reese Witherspoon has a pet peeve.

Five little words: “What do we do now?”

“It’s my most hated question,” Witherspoon said at Monday’s Glamour’s 25th annual Women of the Year Awards at Carnegie Hall, where she received the Hollywood Hero award. “I dread reading scripts that have no women involved in their creation — because inevitably, the girl turns to the guy and says, ‘What do we do now?’”

“I’m serious,” she laughed. “Go back and watch any movie, you will see this line over and over.”

She would know. In 2012, Witherspoon met with seven studio heads and asked them a simple question: “How many movies are you developing with a female lead?”

She was met with blank stares. So she decided to do something about it. She co-founded Pacific Standard with Bruna Papandrea, a production company dedicated to bringing female-driven stories to the big screen.

Pacific Standard’s first two pictures, “Gone Girl” and “Wild,” made more than half a billion dollars at the box office worldwide, and earned stars Rosamund Pike, Laura Dern and Witherspoon herself Academy Award nominations.

A day after Mayor Bill de Blasio declared it “Women of the Year Day,” the gala paid tribute to six individuals and two groups of women who have shaped the year, and the future, with their achievements. Former winners include Hillary Clinton, Amy Poehler, Julia Roberts, Gloria Steinem, Malala Yousafzai, Laverne Cox and Mindy Kaling.

“Over the past 25 years, Glamour has honored 397 women who have helped shape our world,” said Glamour editor-in-chief Cindi Leive. “These women have made life better for all of us. Not that everything’s perfect for women. Congress is stuck at 19 percent female — I believe the technical term is a sausage fest. No, Hollywood doesn’t think it’s a problem to pay Katniss Everdeen less than the dude from ‘The Hangover.’”

“But,” she added, “‘The world only spins forward,’ to quote the playwright Tony Kushner.”

“No mother in the world wants her daughter to have fewer rights than she did,” she added, referring to the fight to keep Planned Parenthood afloat. “It’s up to us to make sure that every single girl in this world can control their bodies and their lives and futures.”

Representing the victims and survivors of the tragic shooting at the Emanuel African Methodist Episcopal Church in South Carolina, which took nine innocent lives, were Alana Simmons, 26, Nadine Collier, 47, Bethane Middleton-Brown, 45, Felicia Sanders, 58, and Polly Sheppard, 71. Presenter Viola Davis, herself from South Carolina, summed up the mood when she tearfully said: “I can’t imagine their pain. I cannot.”

Misty Copeland, the first African-American woman to become principal ballerina at the American Ballet Theater, took home The Showstopper award. “Thank you for honoring a black ballerina,” she said.

Jennifer Hudson and Ellie Goulding both performed. Other notable appearances included Madeleine Albright, Samantha Powers, Serena Williams, Billie Jean King, Iman, Seth Meyers, Judith Light, Jared Leto, Goldie Hawn — and a very dapper Brooklyn Beckham who presented fashion designer, UNAIDS goodwill ambassador and mother Victoria Beckham with the award for Fashion Force.

“I’m so proud of you, and I’m so happy to be here tonight,” he said. “I love you.”

The FIFA Women’s World Cup U.S. national team received the Game Changers award — not only for their big win, but also for their fight to highlight gender inequality in their sport.

Accepting The Entrepreneur award, Elizabeth Holmes, CEO of blood test manufacturing company Theranos, and the world’s youngest self-made female billionaire, gave some advice to the young girls in the room. “Do everything you can to be the best in science and math and engineering,” she said. “Go all into it, and kill the stereotype that we can’t be the best in those fields.”

Surveying the crowd of women, Witherspoon had some advice of her own. Five little words.

“I urge each and everyone of you to ask yourself,” she said, “‘What do we do now?’”

“…although, Amy, I’m 5 years older than you, so I’d probably have to play your grandmother in a movie … by Hollywood standards. And you’ll probably have to play your own mother.”