Descendants 3 is a Disney Channel Original Movie and the third and final installment in the Descendants trilogy. It was announced on February 16th, 2018, during the premiere of Zombies. The film premiered on August 2nd, 2019. The release date was revealed in the description of "VK Day Is Coming", a Descendants trailer. An official trailer was later released on June 17th, 2019.
In Descendants 3, the teenage daughters and sons of Disney's most infamous villains (also known as the villain kids or VKs) — Mal (Dove Cameron), Evie (Sofia Carson), Carlos (Cameron Boyce), and Jay (Booboo Stewart) — return to the Isle of the Lost to recruit a new batch of villainous offspring to join them at Auradon Prep.
When a barrier breach jeopardizes the safety of Auradon during their departure off of the Isle, Mal resolves to permanently close the barrier, fearing that nemeses Uma (China Anne McClain) and Hades (Cheyenne Jackson) will wreak vengeance on the kingdom. Despite her decision, an unfathomable dark force threatens the people of Auradon, and it's up to Mal and the VKs to save everyone in their most epic battle yet.
Mal, Evie, Jay, and Carlos visit the Isle of the Lost to choose four new villain's kids (VKs) to take to Auradon. They pick Dizzy, daughter of Drizella and granddaughter of Lady Tremaine, Celia, daughter of Dr. Facilier, and Squeaky and Squirmy, the twin sons of Mr. Smee ("Good to Be Bad"). The day the kids are to be picked up, Ben, Mal's boyfriend and the king of Auradon, proposes to her. ("Did I Mention (Reprise)") She accepts; Ben's ex-girlfriend Audrey seethes with jealousy and her grandmother Queen Leah admonishes her for failing to secure the family legacy by marrying Ben.
When the barrier is opened for the new VKs, Hades, the god of the underworld, attempts to escape, but Mal beats him back in her dragon form. But before Mal can push him back into the dome, Hades manages to shoot Ben, Carlos, and Jay. That night, unable to contain her jealousy of Mal, Audrey steals the Queen's Crown and Maleficent's Scepter from the Museum of Cultural History ("Queen of Mean"). The theft and Hades' escape attempt has the citizens panicking. Mal, as future Queen, decides the best way to protect the subjects and restore peace is to close the barrier permanently, meaning no new VKs can come, nor can anyone enter the Isle.
Audrey attacks Mal with Maleficent's scepter, turning her into an old hag. Mal and the other VKs go to the Isle to get Hades' ember, the only thing powerful enough to break the scepter's curse, although Mal is restored upon entering the Isle, due to the suppression of evil magic there. Celia gets Mal into Hades' lair, but he thwarts their effort to steal the ember. He is revealed to be Mal's absentee father and reluctantly gives her the ember, warning her that it mustn't get wet and will not exhibit its full powers for her ("Do What You Gotta Do"). While leaving the Isle, Mal and the others are stopped by Uma, Gil, and Harry, who takes the Ember; they agree to help after Mal agrees to release all the children from the Isle.
In Auradon, Audrey attacks Jane's birthday party with a sleeping curse; Chad obsequiously aligns himself with Audrey, while Jane escapes into the Enchanted Lake ("Happy Birthday"). As the entire kingdom falls under Audrey's spell, she offers to reverse it if Ben will marry her; he refuses, so she turns him into a beast and begins turning people to stone. Mal and Uma, vying for leadership of the VKs, return to Auradon with their friends. Despite their bickering, they defeat suits of armor animated by Audrey ("Night Falls"). Uma finds Audrey's diary and learns she spends time at Fairy Cottage, but not without taking a jab at Mal. Evie, nervous to define her feelings for Doug, wakes him with "true love's kiss" ("One Kiss"). Carlos calms Ben, in beast form, until Jane restores him with Enchanted Lake water. Carlos and Jane both apologize for missing her birthday and being worried about each other. As Mal and Uma are thawing towards each other, Audrey traps them in Evie's house; they reverse Audrey's spell by combining their magic, and the kids reunite there.
After reuniting, Carlos gives Jane her birthday gift: a beautiful gold necklace with their names combined that spells out "Jarlos". Carlos says he made it with his 3D printer, and that he could have gone with Cane unless she liked her present. Jane insists she loves it, and Carlos makes an assumption that she doesn't like it. Jane eventually convinces him that she loves it, and lets him put the necklace on her.
At Fairy Cottage, the kids find only a shell-shocked Chad. When Mal admits that she plans to seal off the Isle permanently, the group implodes and Celia, learning she can never see her father again, throws the ember in a birdbath, and Uma and Harry leave. After Evie tells Mal how upset she is for lying to her and their friends, they are all suddenly turned to stone, excluding Mal ("My Once Upon a Time"). Audrey takes Celia hostage and attacks Mal, who turns into her dragon form. Realizing she is Mal's only hope, Uma combines their magic to reignite the ember; Mal overcomes Audrey, who falls comatose, and the curses are lifted. The ember could revive Audrey, but only in Hades' hands; Ben agrees to send for him, while Uma, Harry, Gil, and Celia plan to return to the Isle. Mal apologizes for lying to her friends and former rivals and they forgive her, realizing that she was just trying to do the right thing. Hades arrives and revives Audrey, but decries the double standard by which Audrey is immediately forgiven because she is not considered a villain. Mal and Ben apologize to Audrey; in response, Audrey and Queen Leah apologize to Mal.
Mal announces that she cannot be the Queen of Auradon unless she can also be the Queen of the Isle because everyone is capable of being good and bad. With Ben and the Fairy Godmother's agreement, Mal removes the barrier and creates a bridge, and the people of the newly merged society celebrate ("Break This Down"). In addition, Jane and Carlos become official, Mal and Ben are engaged.
In the mid-credits scene, Mal, Evie, Jay, and Carlos are seen looking at the Isle of the Lost, then racing across the bridge to their parents.
- Dove Cameron as Mal, daughter of Maleficent and Hades.
- Mitchell Hope as King Ben, son of King Beast and Queen Belle.
- Sofia Carson as Evie, daughter of the Evil Queen.
- Booboo Stewart as Jay, son of Jafar.
- Cameron Boyce as Carlos De Vil, son of Cruella De Vil
- China Anne McClain as Uma, daughter of Ursula.
- Sarah Jeffery as Princess Audrey, daughter of Princess Aurora and Prince Phillip.
- Thomas Doherty as Harry Hook, son of Captain Hook.
- Dylan Playfair as Gil, son of Gaston.
- Brenna D'Amico as Jane, daughter of Fairy Godmother.
- Zachary Gibson as Doug, son of Dopey.
- Jedidiah Goodacre as Chad Charming, son of Cinderella and Prince Charming.
- Anna Cathcart as Dizzy Tremaine, daughter of Drizella Tremaine.
- Jadah Marie as Celia Facilier, daughter of Dr. Facilier.
- Christian Convery as Squeaky, son of Mr. Smee.
- Luke Roessler as Squirmy, son of Mr. Smee.
- Jamal Sims as Dr. Facilier, father of Celia. 
- Cheyenne Jackson as Hades, God of the Underworld, father of Mal and ex-husband of Maleficent.
- Linda Ko as Lady Tremaine, grandmother of Dizzy Tremaine.
- Faustino Di Bauda as Mr. Smee, father of Squeaky and Squirmy Smee.
- Dan Payne as Beast 
- Keegan Connor Tracy as Belle 
- Melanie Paxson as Fairy Godmother 
- Judith Maxie as Queen Leah 
- Descendants 3 began filming on May 22, 2018, in Vancouver and wrapped the production on July 16, 2018. Its working title is "The Big Sleep".
- This is the fifth DCOM to receive the third installment, following Zenon: Z3, Halloweentown High, The Cheetah Girls: One World, and High School Musical 3: Senior Year (theatrical release).
- Dianne Doan (who plays Lonnie) is the only original cast member who does not reprise her role for the film.
- The film was leaked online on July 26, 2019. The source was the DVD that someone got early and uploaded online.
- This was Cameron Boyce's last Disney role before his death.
- The film is dedicated to Cameron Boyce. On the night of its release onward, a tribute to Cameron Boyce was added at the beginning and end.
- At the end of Break This Down a couple famous Disney Villains Evil Queen, Queen of Hearts, Captain Hook, Maleficent, Cruella De Vil, Ursula, Gaston, Jafar, Scar (The Lion King), Hades, and Dr. Facilier symbols are shown when people are marching around with a sign of their symbols to represent them.