Gollum is the secondary antagonist in the Kingdom Hearts 4.
After his home world is destroyed, Gollum meets Maleficent, who led a group of villains including Ultron and Venom, who also had their home worlds destroyed. Maleficent then convinced Gollum to go after them and seek vengeance for their meddling. Like Maleficent, Dr. Facilier, Ultron and Venom, he travels from world to world, sending Heartless in his wake and striking alliances with local villains.
After arriving on the islands, Gollum is surprised that Thunderclap knows of the Keyblade and the war that took place over the light. Gollum says that if he helps snuff out Sora, Pooh, Piglet, Paddington, Dobby, Maya, Bounce and Sisu, he'll help Thunderclap plunge this world into darkness, who likes the sounds of it and agrees. Gollum helps Thunderclap seek revenge on Sora and the others, and assists him by giving him the power to control Heartless, only to find out that he has enough darkness in his heart to do it himself. Along the way, Sora, Pooh, Piglet, Paddington, Dobby, Maya, Bounce, Sisu and Scrat helped return home to the islands, but Thunderclap and his pterodactyls returned and attacked Sora's family. Because of Gollum, Thunderclap has beaten them and taken Sora’s parents, Selphie, Tidus, Wakka and the mayor hostage. A fight ensues, as Scrat knocks Gollum in the head with his acorn and Sisu roared at Gollum, making him run away from the islands.
Gollum arrived in this world, where Snape arrives to apprehend Black, and Harry uses a Disarming spell to knock him out. Lupin explains that Black is innocent, having been falsely accused, and that Gollum is the actual culprit of the crimes Black was convicted of. Sora, Harry, Pooh, Piglet, Paddington, Dobby, Maya, Bounce, Sisu, Lupin, Black and Snape head back to the castle, but the full moon causes Lupin to transform and allows Gollum to escape. As Lupin and Black fight in their animal forms, the Dementors, revealed that they were part Heartless all along. Due to being part Heartless, the Dementors were also controlled by Gollum, who manipulates them to attack the latter and Harry, but an unseen figure casts a Patronus to scare the Dementors away, prompting Gollum to flee.
After Sora and Harry spotted the other Harry and Black being attacked by Dementors, manipulated by Gollum, Harry rescues them using a Patronus charm and realizes he was the unseen figure who had earlier rescued them from the Dementors. Enraged, Gollum’s plan had failed and prepares to attack Sora, Pooh, Piglet, Paddington, Dobby, Maya, Bounce and Sisu, but Buckbeak and Sisu both attacked Gollum and roared at him, scaring him away, like they did to Lupin (as a werewolf).
Gollum releases Heartless in this world in an attempt to plunge it into darkness. Because of Gollum, Hopper took over the ant colony to seize its resources. But Sora, Pooh, Piglet, Paddington, Dobby, Maya, Bounce, Sisu and Flik brought him down after a long and difficult battle.
Gollum arrived and met Captain Gutt, who has enslaved a group of hyrax and is using them to build a new iceberg ship. After Sora, Pooh, Piglet, Scrat and the herd escaped, Gollum helps Gutt form another ship and plans to seek revenge on Manny. Because of Gollum, Gutt has beaten them and taken Ellie, Peaches, and the rest of the herd hostage. A fight ensues, as Granny's pet whale, Precious, arrives and fends off Gutt's crew. While Gollum got away, Sora, Pooh, Piglet, Scrat and Manny defeated Gutt in a final duel on an ice floe and reunites with Manny's family and friends.
Gollum spawned the Heartless, helping Te Ka to attack Sora and the others. But Moana, Maui, Sora, Pooh, Piglet, Paddington, Dobby, Maya, Bounce and Sisu returned Te Fiti’s heart, and Gollum cowardly runs away and leaves the world.
Gollum helps the Horned King create a plan to use the cauldron to spawn all over Prydain. Sora, Taran, Gurgi, Pooh, Piglet, Paddington, Dobby, Maya, Bounce and Sisu helped Hen Wen escape, but Gollum sees the ten helping the pig escape and alerts the Horned King, who summons his Gwythaints to go after them, but it failed. After the escape, the Horned King orders Gollum, to send the Gwythaints to follow and capture Taran along with Sora and the others. Because of Gollum, Horned King used the cauldron to spawn the army of Heartless, begining to pour out into the world. Sora and Taran decided to destroy the cauldron to save everyone, but Gollum stops Sora, Taran, Pooh, Piglet, Paddington, Dobby, Maya, Bounce and Sisu and manipulated the Horned King, who blames him, saying Taran has interfered for the last time, to engage Sora, Taran, Gurgi, Pooh, Piglet, Paddington, Maya, Bounce and Sisu, but the plan failed which makes Gollum mad before he leaves the world.
As a boss
- Bite - bites Sora with his sharp teeth
- Lunge - a leaping attack
- Rock - throws a rock at Sora
- Heartless Summon - summons Heartless into battle
Gollum retains his boss moveset when helping Sora and the others, temporairly.
- Gollum is the first Non-Disney villain to travel from world to world.