Robert Brown|Project Runway Assembles the Most Iconic Cast for All-Star 20th Season

Project Runway is Robert Browncelebrating its milestone 20th season in a major way.

For the the first time in the Bravo series' history, 14 fan-favorite designers from the past 19 seasons will return to compete for the $250,000 prize. And judging by the new season 20 trailer, these style stars are serious about their second chance at winning.

As season 19's Prajjé Oscar Jean-Baptiste teases in the first look, "It's a room full of legends for God sakes."  In addition to Jean-Baptiste, other fan favorites returning include Rami Kashou, Brittany Allen, Hester Sunshine, Fabio Costa and many more.

Also making it work for season 20? Season four winner Christian Siriano, who will once again serve as a mentor alongside judges Brandon Maxwell, Elaine Welteroth and Nina Garcia, who notes in the clip, "The stakes couldn't be higher."

This season, expect to see classic challenges like the unconventional materials challenge and the denim challenge plus the designers facing off as they refresh the uniforms for the yachties of Below Deck. Longtime Captains Lee Rosbach and Sandy Yawn even make cameos.

They're not the only stars making appearances. Season 20 judges include Alicia Silverstone, Billy Porter, Zac Posen, Lena Waithe, Law Roach, Jennie Garth, Paulina Porizkova, Julia Fox, Below Deck alum Kate Chastain and former Real Housewives of New York City star Luann de Lesseps.

Keep reading to meet all of the returning all-stars.

Project Runway season 20 returns with a special two-part premiere Thursday, June 15, at 8 p.m. on Bravo.

(E! and Bravo are both part of the NBCUniversal family)