The Lego Movie 2: The Second Part is a 2019 animated adventure comedy film directed by Mike Mitchell and written by Phil Lord and Christopher Miller. Based on the Lego construction toys, it is the fourth and final installment in the Warner Bros. The Lego Movie film series and the sequel to The Lego Movie (2014). Chris Pratt, Elizabeth Banks, Will Arnett, Charlie Day, Alison Brie and Nick Offerman reprise their roles from the first film, with Tiffany Haddish, Stephanie Beatriz and Maya Rudolph joining the cast. The film takes place five years after the events of the previous film and follows Emmet Brickowski, Lucy and their friends, who travel into the Systar System to test their skills and creativity, while Emmet deals with a coming cataclysm known as "Armamageddon".

Development of a sequel to The Lego Movie began in February 2014. In March, it was announced that the film would be directed by Chris McKay and in October it was reported that Lord and Miller would return as the screenwriters. In February 2015, McKay was replaced as director by Rob Schrab, who in turn was replaced in February 2017 by Mike Mitchell, reportedly due to creative differences. Production for the film began in October 2017, with the majority of the cast returning to voice the characters in mid-2018, along with the new cast. As with the previous films in the franchise, the animation was provided by Animal Logic. Mark Mothersbaugh, who composed The Lego Movie and The Lego Ninjago Movie, returned to compose the film's musical score, with artists including Dillon Francis, Beck, Robyn and The Lonely Island providing original songs for the film.

The Lego Movie 2: The Second Part premiered in Los Angeles on February 2, 2019, and was released in the United States on February 8 by Warner Bros. Pictures. It received generally positive reviews from critics, although it was considered inferior to its predecessor. Despite grossing $199.6 million against a budget of $99 million, the film became the franchise's second box office disappointment after The Lego Ninjago Movie. After the film's commercial underperformance, Warner Bros. ultimately let their Lego film rights expire and eventually be picked up by Universal Pictures in 2020, making The Second Part the final installment of Warner Bros.' Lego Movie franchise and the last theatrical film based on the Lego brand until Universal released Piece by Piece in 2024.

Shortly after the destruction of the Kragle via the Piece of Resistance, Duplo aliens arrive and threaten destruction. Emmet builds the aliens a heart as a token of friendship, but one eats it and demands more. Lucy and the Master Builders believe this to be an attack and retaliate, and the ensuing battle ravages Bricksburg. Five years later, a teenage Finn has rebuilt Bricksburg as Apocalypseburg. The city has been ravaged by repeated Duplo attacks, and several people have gone missing while searching for the Duplo home planet. Emmet remains upbeat, in stark contrast to Lucy and his other friends, though he has visions of an impending "Armamageddon".

A mini-doll called General Sweet Mayhem arrives, kidnaps all of Emmet's friends, and takes them to the shape-shifting ruler of the Systar System, Queen Watevra Wa'Nabi. Emmet tries to convince the Master Builders to help him save Lucy and the rest of his friends, but they refuse to help, believing that he is not tough enough to go through the Systar System. Emmet subsequently crafts a spaceship to pursue Mayhem by passing through the "Stairgate". Meanwhile, Watevra has apparently brainwashed Emmet's friends into accepting the joy of her world and convinces Batman to marry her as a way to unite the Lego, Mini-doll, and Duplo worlds. Only Lucy remains skeptical of Watevra's plans.

Emmet's ship is heavily damaged and nearly collides with an asteroid field but is saved by rugged adventurer Rex Dangervest. After hearing Emmet's story, Rex offers to help and takes him to the Systar System. En route, Emmet tries to emulate some of Rex's mannerisms and learn Rex's "Master Breaker" abilities. When they arrive, they quickly reunite with Lucy and learn of the marriage plans, which Rex, Lucy, and Emmet believe to be a front to bring on Armamageddon.

As the wedding starts, Emmet, Rex, and Lucy split up to sabotage the event. Mayhem, who insists the wedding is intended to prevent Armamageddon, intercepts Lucy and explains their true intentions. At the ceremony, Watevra reveals her true form: the heart that Emmet tried to give the Duplo invaders. Realizing that Mayhem was right, Lucy tries to stop Emmet, but he destroys the ceremony with a Master Breaker punch. In reality, Finn, after finding out that his sister, Bianca, had taken his Lego figures, smashes her ceremony creation. Emmet realizes his mistake but is seized by Rex, who reveals he is a version of him from the future, who collided with the asteroids and ended up under a dryer when he was young as Emmet. Embittered and resenting his friends for forgetting him, he changed his name and appearance and created a space time-traveling machine to pick up the raptors and return to help Emmet but to make sure that Armamageddon came to pass as revenge against his friends and everyone who doubted him. When Emmet refuses to abandon his friends, Rex, infuriated at Emmet's "betrayal", usurps and knocks him under the same dryer, ensuring that Rex will continue to exist forever.

In the real world, Finn and Bianca's mother, having had to walk in on them for the past five years and fed up with their bickering jealousy, scolds and orders them to put the Lego toys into a storage bin as punishment; Lucy recognizes this as Armamageddon, which turns out to be "our mama gets in". The Lego worlds began to fall apart as everyone is sucked into a dark void into the storage bin and fear they will not escape.