- Pietro Maximoff (First full appearance) (Leaves Hydra) (Joins team) (Death)
- Wanda Maximoff (First full appearance) (Leaves Hydra) (Joins team)
- Black Widow (Natasha Romanoff)
- Hawkeye (Clint Barton) (Leaves team)
- Iron Man (Tony Stark) (Leaves team)
- Thor (Leaves team)
- Captain America (Steve Rogers)
- Hulk (Dr. Bruce Banner) (Leaves team)
- Vision (First appearance) (Joins team)
- J.A.R.V.I.S (Final appearance) (Becomes Vision)
- Maria Hill
- Dr. Helen Cho (First appearance)
- Laura Barton (First appearance)
- Nick Fury
- F.R.I.D.A.Y. (First appearance)
- Ultron (Only appearance; dies)
- Ultron Sentries (Only appearance) (Destruction)
- Thanos (Cameo)
- Iron Legion (Destruction)
- Zrinka (Only appearance)
- Costel (Only appearance)
- Loki (Mentioned)
- S.H.I.E.L.D. (Mentioned)
- Stark Industries (Mentioned)
- Pepper Potts (Mentioned)
- Stark Relief Foundation (Mentioned)
- Jane Foster (Mentioned)
- Winter Soldier (James Barnes) (Mentioned)
- Howard Stark (Mentioned)
- Stan Lee
- Wanda and Pietro's mother (Mentioned)
- Wanda and Pietro's father (Mentioned)
- Ulysses Klaue (First appearance)
- Intelligencia (Named only)
- Peggy Carter (Illusion)
- Heimdall (Illusion)
- Odin (Mentioned)
- Black Widow Ops Program (Illusion)
- Madame B (Illusion) (First appearance)
- South African Police Service
- South African Army
- Cooper Barton (First appearance)
- Lila Barton (First appearance)
- Dr. Erik Selvig
- Sokovia Policia
- Jocasta (First appearance) (Cameo) (A.I. Disc)
- T.A.D.A.S.H.I. (First appearance) (Cameo) (A.I. Disc)
- Cameron Klein
- Phil Coulson (Mentioned)
- Nathaniel Barton (First appearance) (Appears on a computer screen, TV, or hologram only)
Races and Species:
- Novi Grad
- Hydra Research Base
- Novi Grad
- United States of America
- South Africa
- United Kingdom
- NEXUS World Internet Hub
- South Korea
- U-Gin Genetics Research Facility
- Wakanda (Mentioned)
- Fiji (Mentioned)
- Earth Orbit
- Hel (Mentioned)
- Asgard (Illusion)
- City of Asgard (Illusion)
- Loki's Sceptre
- Hawkeye's Bow and Trick Arrows
- Hawkeye's Suit
- Black Widow's Gauntlets
- Black Widow's Batons (First appearance)
- Black Widow's Suit
- Hydra jetpack
- Hydra energy weapons
- Chitauri Armor
- Iron Man Armor
- Captain America's Shield
- Captain America's Uniform
- War Machine Armor MK II
- Tesseract (Vision)
- Infinity Stones
- Dr. Cho's regeneration cradle
- Tony Stark's New Element
- Exo-7 Falcon (Cameo)
- Infinity Gauntlet (Cameo) (First appearance)
- Captain America's Motorcycle (Harley Davidson Street 750)
- The Churchill derelict ship
- Audi cars
- Veronica (First appearance)
- Harley Davidson LiveWire
- S.H.I.E.L.D. Helicarrier
- Helicarrier lifeboats
In the Eastern European country of Sokovia, the Avengers storm a Hydra fortress with the mission to retrieve Loki's sceptre from Baron Strucker. Meanwhile, the drones of the Iron Legion are on crowd control duty. Strucker decides to surrender, seeing there was no chance of victory. Doctor List protests the decision, suggesting they release the enhanced twins, Wanda Maximoff - who possesses telekinetic and telepathic abilities - and Pietro Maximoff - who possesses superhuman speed. Strucker refuses to risk them, unaware that the twins have already mobilized. Pietro confronts the Avengers outside the base, distracting Clint Barton as he comes under fire from one of Hydra's bunkers, while Wanda remains inside the fortress, which Iron Man and Captain America were able to penetrate. Captain America confronts Strucker and subdues him.
In the outer base, Thor takes the injured Clint Barton back to the quinjet, while Black Widow calms down the Hulk. Inside the base, Iron Man finds the sceptre inside a secret chamber containing Strucker's experiments as he downloads the Hydra scientist's records. As he explores the chamber, Wanda sneaks behind Stark and uses her abilities to make him envision his greatest fear: the bodies of the Avengers strewn about somewhere in deep space as the Earth again comes under attack from the Chitauri; with Captain America's dying breath spent scolding Tony for not saving them, and for not doing his best. Tony eventually snaps out of the vision, and retrieves the sceptre.
The Avengers return to the Avengers Tower in New York. Doctor Helen Cho, an expert in cellular regeneration, takes a look at Barton's injuries. Tony asks Thor if he could study the sceptre before it's taken to Asgard, and the God of Thunder agrees, giving him three days before he departs. Tony starts to study the gem inside the sceptre, and discovers it possess some kind of artificial intelligence far more advanced than his own A.I., J.A.R.V.I.S. Tony convinces Bruce Banner to resume their work on Project Ultron, a peacekeeping program meant to control the drones of the Iron Legion, which could help create peace on the planet in ways the Avengers could not. During a party in celebration for the Avengers' latest victory, Tony leaves the rest of Ultron's syncing process to J.A.R.V.I.S.
The party begins, and the Avengers are joined by other allies, including Sam Wilson, Maria Hill, Helen Cho and Jim Rhodes. During the celebration, Natasha flirts with Banner, and Tony Stark and Thor argue over who has the better girlfriend. Meanwhile, the syncing process finishes, and Ultron awakens, confused by its state of existence. Even though J.A.R.V.I.S. tried to assist Ultron during its first moments of consciousness, the assimilation of all the information on the present world and humanity's history causes it to go haywire. Ultron attacks and seemingly destroys J.A.R.V.I.S. before building itself a body using damaged parts of the Iron Legion.
The party has since wound down, and only the Avengers, Maria Hill, James Rhodes, and Doctor Cho remain. They entertain themselves by taking turns trying to lift Thor's hammer Mjolnir. Though everyone fails, Steve manages to make it budge. Ultron interrupts the friendly competition, and accuses the Avengers of preventing the world from achieving peace by not allowing it to evolve. Ultron believes that the Avengers must be destroyed in order to establish world peace. The advanced A.I. sets numerous Iron Legion drones to attack the Avengers, one of which escapes with Loki's sceptre. Even though Thor destroyed Ultron's body, it used the Internet to escape, taking all of Strucker's data with it.
In Sokovia, Ultron takes over the inner workings of Strucker's now-abandoned base, and builds itself a new body. Using Strucker's data, Ultron learns about the Maximoff twins, and lures them to the church in the center of the small country. Wanda tries to read Ultron's mind, but the twins soon discover Ultron was no human. Ultron then convinces the twins to join his cause to destroy the Avengers.
Back in New York, the team confronts Stark for creating Ultron without their knowledge. Thor scolds Tony for meddling with the sceptre, but Stark claims that they needed Ultron, because no matter how good they do to the world, something like the Chitauri invasion can happen again, and the world needs something as powerful as Ultron was intended to be. All the while, Ultron and the twins have been on the move, building their army, and even killing Baron Strucker, writing the word "PEACE" in his blood on his cell wall. The Avengers deduce that Ultron killed Strucker because he would know what Ultron would do next. The Avengers start investigating the physical copies of Strucker's files, and infer Ultron will want to use vibranium to build itself a stronger body. Vibranium is found in Wakanda, but one of its biggest black market dealers, Ulysses Klaue, operated out of South Africa.
In a salvage yard close to South Africa, the Maximoff twins approach Klaue in his office inside one of the scrapped ships. They try to intimidate him, but as soon as Klaue mentions he would only talk to whomever was in charge of them, Ultron flies up to the office and throws Klaue out of the window, and demands vibranium. When Klaue claims that the vibranium was worth billions, Ultron uses his control over the Internet to transfer large amounts of money to Klaus's different accounts. Ultron is enraged when Klaue compares the A.I. to Tony Stark, and cuts off Klaue's arm at the elbow while venting frustration. The Avengers appear soon after, and a battle breaks out.
Ultron and Iron Man both fly out and continue their fight outside the ship. Inside, Pietro attacks the Avengers, giving his sister the chance to affect them with her powers. The only one who doesn't succumb to her powers of illusion is Clint Barton, who pre-empts her attack with an electrically charged arrow, forcing Pietro to go help her and flee the scene. When he makes a move to get back at Barton, Wanda insists that they continue their mission, and the pair find their next target in the form of Bruce Banner, who was waiting in a quinjet outside the shipyard.
Inside the ship, the different affected Avengers suffer from visions of their fears: Natasha remembers her training in the Red Room, and the way in which she was weaponized and turned into an assassin; Steve sees himself in the 1940s, in a party celebrating the end of the War, where he reunited with Peggy Carter; and Thor envisions himself at a feast in Asgard, where a blinded Heimdall blames him for their destruction. The group eventually snaps out of their visions, albeit traumatized.
Outside the ship, Iron Man finally catches up with Ultron and prepares to destroy his body. However, the villain alerts him of what Wanda Maximoff had caused. The Hulk was unleashed in Johannesburg, completely blinded by rage due to Wanda's manipulation. After destroying Ultron's body, Tony flies towards the city, calling for Veronica, the contingency plan he and Banner had created in case Hulk went out of control. From a Stark Industries satellite, a pod which flies towards Iron Man is released. A bigger suit of armor enfolds around Iron Man, who proceeds to confront Hulk. A furious battle ensues throughout the city. Even though Hulk was capable of tearing apart Iron Man's armor, Veronica sent new parts of the suit to refit it when necessary. After pushing the Hulk through a collapsing skyscraper, Iron Man is finally able to stop him.
The Avengers leave South Africa defeated. Maria Hill contacts the team, and tells them the commotion in Johannesburg had caused a public backlash, and recommends they lay low for a while. Clint takes them to a safe house, a farm in the countryside provided by Nick Fury when he joined S.H.I.E.L.D. The Avengers meet Clint Barton's pregnant wife Laura and their two children, all of whom were omitted from Barton's S.H.I.E.L.D. profile for their own protection. Bruce and Natasha discuss if they should go forward with their relationship, talk about running away once the situation with Ultron was settled. Thor decided to investigate about the things he witnessed in his vision, and departed.
In London, Thor consults Erik Selvig, and both go to the Well of Seeing, a hidden location where people could experience their dreams. Thor steps into the waters of the well, and relives his vision. In addition to his dream of the Asgardian hall, he witnesses images of the Tesseract, the Aether, the Orb, and another of the Infinity Stones, a stone inside Loki's scepter. Lastly, he sees a mysterious figure open its eyes.
Back at the Barton safe house, Steve Rogers and Tony Stark discuss about the latter's methods while chopping wood. Laura interrupts them, and asks Tony if he could take a look at their broken down tractor. When Tony enters the barn, he is confronted by Nick Fury, who subsequently convinces the rest of the Avengers to stand up and fight back against Ultron. Banner deduces that Ultron was going to try to evolve itself, and concluded that he intends to Helen Cho for her expertise with cellular regeneration and her regeneration cradle to build itself a new body using vibranium.
At Helen's Cho research facility in Seoul, she is approached by Ultron, who uses the scepter to compel her to build it a new body using synthetic tissues. Using the Mind Stone inside Loki's scepter, Ultron begins the consciousness transference process into this new body. Wanda Maximoff uses the opportunity to peer into Ultron's psyche and discovers that he was planning to unleash an extinction event on all of humankind, prompting her to cancel Dr. Cho's mind control. The scientist, released from her enslavement, then overrides the transfer, causing Ultron to lash out at her in retaliation. Unable to complete the transfer expediently and with the Maximoff twins' sudden desertion, Ultron takes the android body and flees.
With the Avengers bearing down on Ultron's location once again, the rogue A.I. attempts to evade them in a tractor trailer along with the regeneration cradle and the dormant android body. Captain America arrives at the facility and finds an injured Helen, who informs him of Ultron's plan. The Avengers find the trailer and deploy, with Steve the first to respond. In light of the situation, Ultron is forced to disconnect itself from the cradle to contend with Captain America atop the truck. Black Widow deploys from the quinjet on a motorcycle in pursuit of the trailer. Captain America's battle with Ultron blasts through to the interior of a moving passenger train, and shortly thereafter the Maximoff twins also arrive to add their own resistance to Ultron's assault. Damage to the controls causes the train to derail however, and Ultron escapes while the Maximoffs and Captain America combine their efforts to protect the train's passengers. Meanwhile, Black Widow is still in pursuit of the trailer; managing to gain entry mere moments before two Ultron sentinels take the entire trailer airborne. Natasha directs Barton to get the quinjet behind the truck, and cuts the straps securing the cradle into the truck. The inclination of the truck caused the cradle to fall out of the trailer to be caught by Barton on the quinjet. Before she can jump into the quinjet, Ultron and its sentries grab her and leave. Barton is forced to deliver the cradle to Stark to the Avengers Tower and leave Natasha behind. Captain America is initially relieved once the cradle is confirmed to be route to Stark's hands, but his relief turns to concern when Wanda Maximoff interjects that Stark will only try to use the new body against Ultron.
Ultron returns to Sokovia, where he builds a new body out of vibranium, and imprisons Black Widow in a cell. Meanwhile, in the Avengers Tower, Barton delivers the cradle to Stark and sets out to try to find Natasha, after Stark's suggestion that she might find a way to make contact. The process of transference of Ultron's mind in the new synthetic body was left at 97%, and there were a few minutes left before the body started installing. Tony suggests overwriting the mainframe of the synthetic body with J.A.R.V.I.S., which was revealed as the cause to Ultron being unable to access the nuclear codes. J.A.R.V.I.S. had survived Ultron's initial attack and went into hiding in the Internet, proceeding to thwart the robot's efforts until discovered by Stark. When Captain America and the twins arrive at the Tower, they try to stop the upload, fearing Tony could unleash something as bad as Ultron. The dispute escalates to a physical confrontation, but it is interrupted when Thor returns. Using Mjolnir's power, the God of Thunder finishes powering up the cradle, and the synthetic body comes to life. It initially Shoves Thor violently away, but quickly calms down at the sight of New York's buildings and lights. Thor explains to the rest of his teammates about the figure that had appeared in his vision. The android states that he has no desire to destroy Ultron, but he must take the side of life and to protect life he would have to destroy the robot. The android proves his worth to the team when he casually lifts Mjolnir and hands it to Thor. Shortly thereafter, Barton tells them that he found Natasha in the Hydra base in Sokovia, where the team, the android and the twins included, prepare to go.
Their first course of action is to start evacuating civilians from the city While Thor and Banner go to rescue Natasha. Iron Man confronts Ultron inside the church in the center of the city while the android, now thought of as the "Vision" in light of Thor's dream, gets inside Ultron's systems and cuts it off from the Internet, preventing it from transferring its mind to yet another body. Bruce Banner finds and frees Natasha, and informs her about the ensuing battle, suggesting to her that they leave. The two share a kiss, but Romanoff pushes Banner down a shaft to awaken the Hulk, musing that she needs "the other guy." They then leave the base to help the rest of the team.
As the Avengers are helping the civilians out of Sokovia, the ground starts to rumble. A portion of Sokovia rises into the air. Ultron had used his remaining vibranium to create a set of machines capable of lifting the city into the sky high enough that it would cause an extinction level event when it falls back to the Earth. The mechanism is powered by a drill in the center of the church, and creates a magnetic field that holds the portion of Sokovia together. Iron Man informs Captain America that if the drill is overcharged, it could blow up the makeshift asteroid, preventing it from threatening the Earth if it fell. Cap refuses to let this happen until the all of the civilians trapped on the rock are evacuated. Suddenly, the old S.H.I.E.L.D. helicarrier appears in the distance, commanded by Nick Fury and run by the remains of S.H.I.E.L.D. Numerous "lifeboats" are dispatched to pick up the civilians and take them to the safety of the helicarrier.
The Avengers reassemble at the church to fight off Ultron long enough to ensure the complete evacuation of the airborne rock. The Avengers are victorious, and Ultron's main body is heavily damaged in the process. Numerous sentries try to attack the helicarrier, but Nick Fury deploys Rhodes in the War Machine armor to get rid of them. Ultron's prime body reaches the Avengers quinjet and uses its firepower to attack the Hulk before flying off to harass other targets. It finds one when Clint Barton rushes to rescue a boy, but before the quinjet's guns can find their target, Pietro puts himself between them, sacrificing himself to shield Hawkeye and the child from the barrage. The Hulk retaliates shortly thereafter, leaping into the quinjet and hurling Ultron's prime body down to the streets below. Wanda Maximoff finds the wrecked form of the robot in the wreckage of a bus, and tears out its core in a symbolic gesture to demonstrate how the death of her brother broke her own heart. The Avengers proceed to the lifeboats once every civilian had already boarded them.
One of the last remaining Ultron sentries reaches and activates the drill, plunging the floating portion of Sokovia towards the Earth. Iron Man and Thor manage to overcharge the drill, causing the airborne fragment of Sokovia to be blasted apart. The Hulk remains in the quinjet and severs the radio link from the helicarrier, silencing Natasha's pleas to help her find him.
On the ground, Vision finds the Ultron's last remaining body, a badly-damaged drone. Ultron confronted Vision, ensuring him that killing it wouldn't make a difference, as humans are set on a path of self-destruction. Vision replies him that he knew, but that it is the flaws of humankind that made them graceful, and he finds it a privilege to live among them. The sentry charges at Vision, but he destroys it with a blast of energy from the Mind Stone.
After the conflict, a New Avengers Facility is established in upstate New York, run by Nick Fury, Helen Cho, Maria Hill and Erik Selvig. Tony Stark retires from the team, and Clint returns to his family, which now includes his newborn son Nathaniel Pietro Barton. Thor believes the Mind Stone is secure with the Vision, and returns to Asgard. Nick Fury tells Natasha that an unidentified object, possibly the quinjet Hulk escaped in, was found in the ocean. Captain America and Black Widow appear before War Machine, Falcon, Vision, and Wanda - the new Avengers.
On the other side of the galaxy, Thanos opens a vault containing the Infinity Gauntlet. Dissatisfied with his pawns' failures, the Mad Titan dons the Gauntlet, resolved to retrieve the Infinity Stones himself.
- Paul Bettany as The Vision, an A.I. programmed by Tony Stark and Bruce Banner to aid the Avengers in fighting Ultron.
- Bettany also voices J.A.R.V.I.S for the final time.
- Claudia Kim as Dr. Helen Cho, a world-renowned geneticist whose work keeps the Avengers fighting.
- James Spader as Ultron, a computer program Tony Stark found in Chitauri technology left behind after their attack on New York City that Stark turned into a sophisticated A.I.
Andy Serkis and Julie Delpy appear in minor roles as Ulysses Klaue, a South African arms dealer and former acquaintance of Tony Stark, and Madame B, a character who trained Black Widow in the Red Room, respectively. Stan Lee makes a cameo appearance as an Avengers party member. Henry Goodman portrays Doctor List. Kerry Condon voices F.R.I.D.A.Y., the A.I. Tony Stark uploads to his armor to replace J.A.R.V.I.S. Aaron Himelstein reprises his role as Cameron Klein. Josh Brolin makes an uncredited appearance as Thanos in the mid-credits scene.
- The title of the film was confirmed at San Diego Comic Con 2013.
- This film became the 21st film to pass $1 billion at the worldwide box office. With a worldwide total box office gross of about $1.4 billion, this film became the 4th-highest-grossing film of 2015, and at its peak the 5th-highest-grossing film of all time.
- During the movie's production, it was considered to have the Hulk turn grey when under the Scarlet Witch's mental manipulation. The movie's VFX supervisor Christopher Townsend explained the idea was eventually dropped to avoid confusing the audience "in creating a new character, per se."
- Spider-Man could have appeared in the film's final scene when a new team of Avengers is assembled if the deal between Sony Pictures and Marvel Studios to include the character in the latter's films had been made sooner, according to director Joss Whedon.
- A relationship between Black Widow and Hawkeye was planned. Joss Whedon fought against it to show that men and women can be great friends without being in a relationship.
- The romance between Natasha Romanoff and Bruce Banner had been planned since Marvel's The Avengers.
- There were two alternate versions for the scene between Natasha and Bruce at Clint Barton's farm, one would have consisted of Bruce rejecting Natasha, and the other consisted of Natasha bringing out the Hulk.
- Whedon decided to kill one of the Maximoff twins believing the death of a young character would be more striking. And he chose Quicksilver because he didn't want to kill the only other female protagonist of the movie.
- Joss Whedon tried to keep Quicksilver's death a surprise by announcing Aaron Taylor-Johnson had a three-picture contract.
- An alternate cut of the movie had Quicksilver survive the barrage of bullets and recover with Helen Cho's technology. He would've joined the new Avengers with a new uniform, alongside Wanda.
- A subplot consisting of Hawkeye being unable to finish building a tool shed because of being always off with the Avengers is featured in deleted scenes.
- In the original cut, the spirits in the Well of Seeing would've possessed Thor, and Selvig would've asked them to interpret the God of Thunder's dreams. The scene was ultimately changed as it was not well-received by test audiences.
- Thor was also originally going to have two visions. The second one featuring Loki in a burning Asgard. The God of Mischief would've asked Thor "Oh, what would father say?", and his current position in the throne of Odin would have been referenced. Tom Hiddleston was originally reported to return as Loki in this film.
- Marvel Studios executives didn't want to include the scenes depicting the team's visions, or Hawkeye's farm. The latter was once left in when Whedon agreed to cut the cave subplot to the minimal requirement to move the plot along.
- Marvel Studios and Sony Pictures discussed integrating Spider-Man's mythos into the movie by adding the the OsCorp Tower to the New York City skyline, but agreements weren't made in time.
- Whedon planned for the Avengers to go to Sokovia in the film's final act still at odds with each other, only truly coming together during the church fight.
- The original script called for the Quinjet in which Hulk fled to reach the stratosphere, and for Hulk to see the stars, to indicate he was "leaving the world behind." The idea was scrapped because Marvel Studios didn't want people being led to think of a possible adaptation of Planet Hulk, a Hulk storyline in which he's sent to another planet.