The 15th and final season of "American Idol" is coming to an end, but the hit singing competition show plans to go out with a bang!

Fox announced on Thursday that Grammy-winning "American Idol" alum Kelly Clarkson and Carrie Underwood will return to perform during the three-night grand finale, which kicks off on Tuesday, April 5 with a 90-minute retrospective.

"The can't miss, 90-minute retrospective will feature host Ryan Seacrest, current and former judges, former IDOLs and contestants and behind-the-scenes team sharing their person IDOL memories, as they reflect on what the show has meant to them and how it became the groundbreaking series that it is today," Fox said. "In addition to Seacrest, original IDOL judges Simon Cowell, Paula Abdul and Randy Jackson offer never-before-revealed stories about how Idol came to be. This is a very special, inside look at the journey that IDOL has taken viewers on during its 15-season run."

The announcement then explains that Clarkson, who was the first-ever "Idol" winner, and Underwood, who won season four, will return to the stage "one last time" to perform on the final night, Thursday, April 7. Clarkson reportedly pre-taped her finale performance because she's expecting to give birth to her second child soon, although this has not yet been confirmed.

Along with Clarkson and Underwood, several other "Idol" all-stars will take the stage before the final Idol is crowned, including Fantasia, Ruben Studdard, Taylor Hicks, Jordin Sparks, David Cook, Kris Allen, Lee DeWyze, Scotty McCreery, Candice Glover, Caleb Johnson, Nick Fradiani, Allison Iraheta, Amber Holcomb, Blake Lewis, Bo Bice, Bucky Covington, Brandon Rogers, Casey James, Carly Smithson, Chris Daughtry, Clark Beckham, Clay Aiken, Colton Dixon, Constantine Maroulis, Danny Gokey, Diana DeGarmo, Elliott Yamin, Ace Young, George Huff, James Durbin, Jessica Sanchez, Joshua Ledet, Justin Guarini, Katharine McPhee, Kellie Pickler, Kimberley Locke, Kree Harrison, LaToya London, Lauren Alaina, Melinda Doolittle, Pia Toscano, Sanjaya, Skylar Lane, Tamyra Gray and more.

The three-night event will begin with the retrospective special on April 5 from 8 p.m. to 9:30 p.m. ET with the actual two-night finale airing live on April 6 from 8 p.m. to 9 p.m. ET and April 7 from 8 p.m. to 10:06 p.m. ET.