Longoria, 42, and Witherspoon, 41, are just two of the powerful A-listers who plan to put their "Time's Up" initiative into action on Sunday by walking the red carpet with other actresses who are also backing up the movement.
Golden Globes 2018: What to Expect as Celebs Hit the Red Carpet in All Black
Additionally, expect to see a lot of black on the red carpet, in protest of sexual harassment and misconduct in Hollywood, and everyone wearing the official "Time's Up" pin, created by Nocturnal Animals costume designer and stylist Arianne Phillips.
"This is a moment of solidarity, not a fashion moment," Longoria explained to The New York Times. "For years, we've sold these awards shows as women, with our gowns and colors and our beautiful faces and our glamour."
"This time the industry can't expect us to go up and twirl around," she added. "That's not what this moment is about."
Hosted by Seth Meyers, the Golden Globes will broadcast live from The Beverly Hilton in Beverly Hills, California, on Sunday at 8 p.m. ET/5 p.m. PT on NBC. Hear more on "Time's Up," and everything we know about the awards show so far, in the video below.