Jennifer Garner, Michelle Obama: 25 Women Changing the World

01 of 19

JENNIFER GARNER & CAROLYN MILES

Jennifer Garner - 25 Women — Amanda Marsalis

For eight years, Garner has served as an artist ambassador and is now a trustee for Save the Children, which provides relief and support for kids in rural America and developing countries. "Becoming a mother just automatically crosses any boundary you might have with another woman. It's like joining this huge, enormous global club. When you see somebody struggling, you instantly think, 'Well, that could be me,' " she says. Adds Miles (left), CEO of Save the Children, "This is a personal passion for Jennifer. She understands what we do and what the challenges are. Every child has huge potential."

02 of 19

CHARLIZE THERON

Theron started her eponymous Africa Outreach Project in 2007 to help eradicate AIDS in her home nation of South Africa. As a kid, "I remember people dying and people not knowing why they died and people always whispering this word — it was happening right in front of me," she says. "It was taboo in that country to talk about things like safe sex. [Today], I see children so active in the conversation."

03 of 19

SHERYL SANDBERG

"We've all heard the myth that women don't support each other," says Sandberg. "But it's not true. Women are incredible allies." The Facebook COO outlines several ways to advocate for the women in our lives, including celebrating each other's accomplishments. "When women celebrate one another, we're all lifted up," she shares.

04 of 19

BARBARA BUSH

The daughter of former President George W. Bush and former First Lady Laura, Bush (right) cofounded Global Health Corps to cultivate the next generation of leaders in ensuring equitable health care around the world. "There are plenty of issues to work on. If they were easy to solve, we would have solved them," she says. "Use curiosity as your driver and listening as your biggest skill."

05 of 19

SYBRINA FULTON

When Fulton's unarmed 17-year-old son Trayvon Martin was fatally shot by a neighborhood watchman in 2012, she made it her life's mission to advocate against senseless shootings in America. "I want to touch lives to save lives," says Fulton, who founded the Trayvon Martin Foundation two months after her son's death sparked national outrage. "Weapons can shake entire communities," she says of the country's gun violence epidemic. "It's important to empower and educate families."

06 of 19

SALMA HAYEK

Hayek, a powerful voice for women's rights, is a strong advocate for refugees and recently began sponsoring a small orphanage in Tijuana, Mexico. "One woman saw so many kids suffering in the streets and started taking them in," says the Mexico-born star. "These children are sexual-violence victims, and the majority are orphans from the drug wars in Mexico."

07 of 19

YUSRA MARDINI & QUEEN RANIA

Yusra Mardini and Queen Rania - 25 women — COURTESY QUEEN RANIA

The Jordanian monarch (right) tells PEOPLE of Mardini's brave battle last year, fleeing her home in Syria and having to hop out and push her fellow refugees on their broken-down dinghy through the Aegean Sea toward Greek shores. "She would, literally, have to swim for her life," Queen Rania shares of the 2016 Olympian. For her part, Mardini says, "A lot of people on the boat said, 'You're really brave.' I said, 'Just shut up until we arrive!' "

08 of 19

KATHERINE JOHNSON

Known to her NASA colleagues as the "human computer," the renowned mathematician — who became the first African-American woman to desegregate her West Virginia graduate school — calculated the trajectory for Alan Shepard's first trip into space in 1961. Her advice for young women? "Find out what your dream is and work at it," says Johnson, who inspired the upcoming film Hidden Figures.

09 of 19

KENDRA HEUER

"My life has been ruined without my consent," Heuer read aloud at her assailant's sentencing hearing in August in a Boulder, Colorado, courtroom. Two years earlier, during her freshman year at the University of Colorado, she was attacked by a fellow student who was later found guilty of sexual assault. Her powerful statement — and the judge's sentence of no prison time — made headlines nationwide. Now Heuer is revealing her identity for the first time. "If someone reads my story and sees that I'm not ashamed, maybe they won't be," she says. "I think about the person who did this to me, and I won't let him win. I want my voice to be heard. I'm a survivor."

10 of 19

NATALIE PORTMAN

The Oscar winner and mother supports WE, a charity that fights poverty around the world, building schools and "everything that goes around them," she says, including wells, latrines, micro-finance for mothers and access to doctors. Visiting Kenya last year opened the star's eyes. "I think that an awareness of the world and caring for other people is the No. 1 thing you hope to impart to your own family," she shares.

11 of 19

JULIA LOUIS-DREYFUS

"My stepfather [L. Thompson Bowles] was a surgeon, and he worked for an organization called Project HOPE. We lived in Sri Lanka, Colombia, Tunisia. It was part of our upbringing that you 'are connected to those around you,' " she says. A strong supporter of the Natural Resources Defense Council, the Veep star was inspired after hearing Bobby Kennedy speak on the group's work. "Climate change is here. The NRDC champions not only for the earth's resources but for the people who are in danger of losing them, of having these fundamental rights taken from them."

12 of 19

KATIE MEYLER

Nothing could have prepared Meyler for what she saw when she first landed in Liberia as a 23-year-old volunteer: little girls on the street selling their bodies for water. "I decided then that I was going to help these girls," says Meyler. She started More Than Me, an organization dedicated to using education as a catalyst for change, and in 2013 opened the first tuition-free all-girls school in Liberia. Now, with the help of the Ministry of Education, Meyler is opening more schools in the country.

13 of 19

SERENA WILLIAMS & AJA BROWN

Serena Williams Mayor Aja L. Brown - 25 Women — Clive Brunskill/Getty; Inset: Johnny Nunez/Getty

As models walked the runway for her fall fashion show in September, the Wimbledon champ read a poem titled "I Am Woman." "I wanted to empower women to feel strong and feel amazing," she says. It's a message she's bringing to her hometown of Compton, California, where she and Mayor Aja Brown (inset) are opening the Yetunde Price Resource Center, named after Williams's oldest sister. (She was killed by gang violence in 2003.) "We have both lost family members to violence," adds Brown. "The goal of the center is to treat post-traumatic stress syndrome and to be proactive about the importance of mental health and wellness."

14 of 19

NICOLE HOCKLEY

77th Annual Golden Globe Awards - Arrivals

"Dylan is with me every day in my heart," Hockley says of her 6-year-old son, who was killed at Sandy Hook Elementary in 2012. "The more I learned about his death, and the person who took his life, I recognized there were signs for years and multiple opportunities for intervention." Sandy Hook Promise, the group she helped found, teaches students and adults how to recognize the signs of people at risk of hurting themselves or others. "Gun violence is preventable if you know the signs."

15 of 19

MAISIE WILLIAMS

The Game of Thrones actress faced bullying in school and today focuses on how younger generations can make social media a positive place. "People say, 'Oh, that's so strange that you got bullied.' And I'm like, 'It's so strange that anyone gets bullied,' " she says. "We are the most developed generation in terms of talking about difficult subjects. That's what I love about us."

16 of 19

OPRAH WINFREY

The media mogul praises two other brave women: Zainab Salbi (left) and Maria Eitel (inset), who founded Women for Women International and Girl Effect, respectively. Salbi, who works for female rights in war-torn countries, "is one of the bravest women I know," says Winfrey. "Her life is threatened all the time, but she feels that giving women a voice is the most important thing." Of Eitel, she "understands you've got to change the way the girl sees herself and the way her community sees her in order to bring about full empowerment," Winfrey shares.

17 of 19

LINDSEY VONN

When Vonn was 9, she got Olympic ski racer Picabo Street's autograph in Minneapolis. "It was like meeting a superhero," says Vonn. "Those two minutes changed my perspective and made me want to be an Olympian." Now the gold medalist is doing the same for girls she mentors through the Lindsey Vonn Foundation, which launched last year. "I want to empower young girls and inspire them in as many ways as we can," she adds.

18 of 19

MELISSA MAYS

It's been two years since Mays learned that the water coming out of her faucets in Flint, Michigan, was contaminated with dangerously high levels of lead — and there's still work to be done. "If you know something is wrong, you stand up — that's what I talk about with my kids," says the mom of three, who cofounded Water You Fighting For to get answers on current lead levels and inform fellow citizens.

19 of 19

FIRST LADY MICHELLE OBAMA & DR. JILL BIDEN

Michelle Obama Jill Biden - 25 Women — ROBYN BECK/AFP/Getty; Cheriss May/NurPhoto via Getty

Though they've both accomplished a lot during their eight years in D.C., together, they created Joining Forces, which supports U.S. veterans and their families. "She has been the most extraordinary partner," the First Lady tells PEOPLE of Biden, who reciprocates the kind words. "Naturally, freely, warmly, she brings joy and hope, often simply through a hug, to the deployed, caregivers and wounded warriors."