Singer Halsey lit up a crowd of Women's March protesters in New York City on Saturday (20Jan18) by reciting a moving poem she penned for the occasion.

Thousands of marchers took to the streets on the one-year anniversary of U.S. President Donald Trump's inauguration to call for an end to sexual harassment in support of the #MeToo and Time's Up movements, in addition to taking on several other critical agendas, such as environmental sustainability, civil rights and the protection of immigrants.

The 23-year-old Now or Never hitmaker was among the celebrities in the Big Apple who spoke to the crowd at the large gathering and she shared a powerful poem she wrote during her riveting speech that encouraged others to embrace the possibility of living in a more equal world.

“This is the beginning, not the finale, and that’s why we’re here, that’s why we rally," she concluded at the podium to a lit up crowd.

Halsey shared her speech in its entirety in a video clip on her Twitter account later in the day, admitting it was difficult for her to address fellow protesters.

"This was really hard for me to do but I’m glad I did it," she tweeted. "Thank you guys. This is why we rally. #WomensMarch2018".

"If you’re supporting from anywhere in the world, the streets, your home, your job: We thank you," Halsey added in another message.

The pop star wasn't the only A-lister out marching in solidarity with Women's March protesters. Stars like Natalie Portman, Viola Davis, Mila Kunis and Allison Janney took to the streets in Los Angeles for the Southern California branch of the international Women's March protest, which took place in several other large U.S. cities, as well as Rome, Italy.

Former child actress Portman moved the crowd during her speech in L.A. by sharing a deeply personal experience of being sexualised as a young teen after she starred in 1994 thriller Leon: The Professional.

"I excitedly opened my first fan mail to read a rape fantasy that a man had written me," the 36-year-old recounted. "A countdown was started on my local radio show to my 18th birthday, euphemistically the date that I would be legal to sleep with. Movie reviewers talked about my budding breasts in reviews.

"I understood very quickly, even as a 13-year-old, that if I were to express myself sexually, I would feel unsafe and that men would feel entitled to discuss and objectify my body to my great discomfort."

Portman added: "At 13 years old, the message from our culture was clear to me. I felt the need to cover my body and to inhibit my expression and my work in order to send my own message to the world: that I'm someone worthy of safety and respect."

Natalie concluded her speech by calling on her fellow protesters to serve up their continued support for Time's Up.

Longtime activist Jane Fonda, rapper Common, Creed actress Tessa Thompson, Lena Waithe, all-star women's rights attorney Gloria Allred and others also did their part to support the movement by leading the Respect Rally at the Sundance Film Festival in Utah.