Women in Hollywood are welcoming the new year with resolution.

In response to the sexual harassment allegations that rocked the industry in 2017, Reese Witherspoon, Eva Longoria, Shonda Rhimes, Ashley Judd and Natalie Portman and hundreds of others have unveiled Time's Up, an initiative dedicated to confronting abuse of power and promoting workplace equality.

Monday's announcement was accompanied by a pledge of support to working-class women in an open letter signed by hundreds of women in show business, many of them A-listers, in a full-page ad in The New York Times and the Spanish-language newspaper La Opinion.

“It's very hard for us to speak righteously about the rest of anything if we haven't cleaned our own house,” Scandal creator Shonda Rhimes tells the Times. “If this group of women can't fight for a model for other women who don't have as much power and privilege, then who can?”

Initiated by a group of female agents in Hollywood, Time's Up has about 300 members. Other high-profile supporters include Rashida Jones, Kerry Washington, Lena Waithe and America Ferrera; executives Donna Langely and Katie McGrath; creatives Melina Matsoukus and Jill Soloway; and lawyers Nina Shaw, Tina Tchen and Anita Hill.

The group's open letter noted that its members realized their reach may help others, saying: "We also recognize our privilege and the fact that we have access to enormous platforms to amplify our voices. Both of which have driven widespread attention to the existence of this problem in our industry that farmworker women and countless individuals in other industries have not been afforded."

The letter acknowledges early support from Alianza Nacional de Campesinas (the National Farmworker Women's Alliance) after the floodgates opened on news about sexual harassment and abuse of power in Hollywood. Among the entertainment industry power players accused recently: Harvey Weinstein, James Toback and Dustin Hoffman.

After Monday's announcement, other members of the movement, including Amber Tamblyn, Viola Davis and Alyssa Milano, spread the word on social media. They were joined by Justin Timberlake and former National Security Advisor Susan Rice.

Timberlake, who is married to actress Jessica Biel, tweeted: "No more accepting sexual harassment and inequality at work as normal. It's NOT normal."

His wife, who is part of the Time's Up organization, echoed his message: "Let's all make this resolution for the year: No more accepting sexual harassment and inequality at work as normal. It's NOT normal."

Tamblyn's social media post described the group's message as an "open call to arms."

Viola Davis tweeted: "I stand with women across every industry to say #TIMESUP on abuse, harassment, marginalization and underrepresentation."

Alyssa Milano explained in her tweet that the group wants survivors of abuse to get the support they need.