Credit: Neilson Barnard/Getty Images; Jim Spellman/WireImage; Slaven Vlasic/Getty Images

As the coldest month of the year, December may not seem like the most obvious time to tap your dress collection. But Debra Messing, Shailene Woodley, Lola Kirke, Jennifer Morrison, and Dressember founder Blythe Hill want you to do so anyway.

Not to be confused with last month’s Movember and that abundance of male facial hair that we tolerated or adored (for a good cause, of course!), Dressember is all about honoring the strength and beauty of womanhood by wearing a dress each day during the last month of the year. But, more importantly, it’s also about raising awareness and the funds to help fight human sex trafficking.

Dressember actually started eight years ago, when Hill, the non-profit's founder, decided to challenge her creativity by wearing a different dress every day for a month. The idea caught on among friends and friends of friends, and in 2013, she had a light bulb moment: why not use this particular brand of girl power to raise money for a cause she was passionate about. To date, the campaign has raised $3.5 million to fight sex trafficking.

This year, a host of celebrities has joined Hill's cause. Clad in the Dressember Collection’s “Brit” dress, Shailene Woodley posted an image to her Instagram, naming one reason why it's #ItsBiggerThanADress: of the more than 30 million people currently enslaved, 2 million are children. Scroll down to see who else joined in.

Dressember's own collection of dresses (sold through Elegantees) includes five styles—Penny, Brit, Blythe, Sierra, and Jessica—designed by five different women, including Anne Hathaway and Rose Byrne’s stylist Penny Lovell, and created by survivors of sex trafficking in Nepal, earning them two-to-three times the local minimum wage.

We also love the flowing maxi dress Debra Messing wore to tout the campaign on her feed.

Kirke posted, “Dresses help me to get in touch with the sacred feminine. I love the Dressember dress collection because it partners with a sewing center in Nepal to make these ethically made dresses.” She called the month “an invitation to celebrate brave women everywhere who are resisting this kind of violence.”

Melissa Joan Hart says, “I’m generally a jeans and t-shirt girl, so wearing a dress is the ultimate in feeling feminine for me.” She chose to buy the Penny from Dressember's collection because of it’s versatility. “I can easily pair a shoe and some jewelry with it and I’m all set.”

Laura Harrier, who’s new film Fahrenheit 451 premieres on HBO in the spring and is currently shooting Black Klansman with Spike Lee, posted: “I became involved to help bring awareness to a domestic and international issue that affects millions of people every year.”

Choosing to wear the Britt, actress Joanna Gacia Swisher, who stars in Kevin (Probably) Saves the World, struck a pose for the cause.

And not only will you spot Jennifer Morrison (former Once Upon A Time actress) in dresses every day this month to combat modern-day slavery, but you're invited to join her team, pledging to help them raise $10,000.

Create your own Dressember squad of anti-trafficking warriors by setting a goal to share with your family and friends and donating here. Or buy yourself a new party dress from Dressember's collection; a portion of the proceeds will benefit survivors of sex trafficking in Nepal. The money raised for the challenge will be granted to human rights organizations, the International Justice Mission (IJM), and A21.

What do you say—time for an LBD?