Avengers: Age of Ultron is a 2015 American superhero film based on the Marvel Comics superhero team the Avengers. Produced by Marvel Studios and distributed by Walt Disney Studios Motion Pictures, it is the sequel to The Avengers (2012) and the 11th film in the Marvel Cinematic Universe (MCU). Written and directed by Joss Whedon, the film features an ensemble cast including Robert Downey Jr., Chris Hemsworth, Mark Ruffalo, Chris Evans, Scarlett Johansson, Jeremy Renner, Don Cheadle, Aaron Taylor-Johnson, Elizabeth Olsen, Paul Bettany, Cobie Smulders, Anthony Mackie, Hayley Atwell, Idris Elba, Linda Cardellini, Stellan Skarsgård, James Spader, and Samuel L. Jackson. In the film, the Avengers fight Ultron (Spader)—an artificial intelligence created by Tony Stark (Downey) and Bruce Banner (Ruffalo)—who plans to bring about world peace by causing human extinction.

A sequel was announced in May 2012 after the successful release of The Avengers, with Whedon set to return as writer and director in August. He updated Ultron's origin for the film to involve the MCU's Avengers team and introduced the characters Pietro (Taylor-Johnson) and Wanda Maximoff (Olsen), to whom Marvel shared the rights with 20th Century Fox. Casting began in June 2013 with Downey re-signing. Second unit filming began in February 2014 in South Africa, with principal photography taking place between March and August, primarily at Shepperton Studios in Surrey, England. Additional footage was filmed in Italy, South Korea, Bangladesh, the state of New York, and around England. With an estimated net production budget of $365 million, the film is one of the most expensive ever made.

Avengers: Age of Ultron premiered in Hollywood, Los Angeles, on April 13, 2015, and was released in the United States on May 1, as part of Phase Two of the MCU. The film received generally positive reviews from critics and grossed over $1.4 billion worldwide, becoming the fourth-highest-grossing film of 2015 and the fifth-highest-grossing film of all time during its run. Two sequels have been released: Avengers: Infinity War (2018) and Avengers: Endgame (2019).

In the Eastern European country of Sokovia, the Avengers—Tony Stark, Thor, Bruce Banner, Steve Rogers, Natasha Romanoff, and Clint Barton—raid a Hydra facility commanded by Baron Wolfgang von Strucker, who has experimented on humans using the scepter previously wielded by Loki. They are attacked by two of Strucker's test subjects, twins who have been given superhuman abilities: Pietro (superspeed) and Wanda Maximoff (telepathy and telekinesis). The Avengers apprehend Strucker and retrieve Loki's scepter.

Stark and Banner discover an artificial intelligence (AI) within the scepter's gem and secretly use it to complete Stark's "Ultron" global defense program. The unexpectedly sentient Ultron, believing he must eradicate humanity to save Earth, eliminates Stark's AI J.A.R.V.I.S. and attacks the Avengers at their headquarters. Escaping with the scepter, Ultron uses the resources in Strucker's Sokovia base to upgrade his rudimentary body and build an army of robot drones. He kills Strucker and recruits the Maximoffs, who hold Stark responsible for the deaths of their parents by his company's weapons. The trio go to the base of arms dealer Ulysses Klaue in Johannesburg to get vibranium. The Avengers attack them there and are subdued by haunting visions created by Wanda. Banner turns into the Hulk and rampages through Johannesburg until Stark stops him with his anti-Hulk armor.

A worldwide backlash over the Hulk's destruction, and the fears Wanda's hallucinations incited, send the team into hiding at Barton's farmhouse with his family. Thor departs to consult with Dr. Erik Selvig on the apocalyptic future he saw in his hallucination, while Nick Fury arrives and encourages the team to form a plan to stop Ultron. In Seoul, Ultron uses Loki's scepter to enslave the team's friend Helen Cho. They use her synthetic-tissue technology, vibranium, and the scepter's gem to craft a new body. As Ultron uploads himself into it, Wanda reads his mind and discovers his plan for human extinction; the Maximoffs turn against Ultron. Rogers, Romanoff, and Barton fight Ultron and retrieve the synthetic body, but Ultron captures Romanoff. Stark and Banner upload J.A.R.V.I.S., who has been secretly active inside the Internet to hide from Ultron, into the synthetic body.

The Avengers fight among themselves over the decision to upload J.A.R.V.I.S. until Thor returns and helps activate the body. He explains that the scepter's gem is part of his vision, related to the powerful six Infinity Stones, from which the new being gets the name "Vision". He earns their trust by being worthy of lifting Thor's hammer, Mjölnir. Vision and the Maximoffs go with the Avengers to Sokovia, where Ultron has used the remaining vibranium to build a machine to lift a large part of the capital city into the sky, intending to crash it into the ground to cause global extinction. Banner rescues Romanoff, who awakens the Hulk for the battle. The Avengers fight Ultron's army while Fury arrives in a Helicarrier with Maria Hill, James Rhodes, and S.H.I.E.L.D. agents to evacuate civilians.

Pietro dies when he shields Barton from gunfire, and a vengeful Wanda abandons her post to destroy Ultron's primary body. This allows one of his drones to activate the machine, causing the city to plummet. Stark and Thor overload the machine and shatter the landmass. The Hulk, unwilling to endanger Romanoff by being with her, departs in a Quinjet. Vision confronts and destroys Ultron's last remaining drone. After the Avengers establish a new base, Thor returns to Asgard to learn more about his vision. As Stark leaves and Barton retires, Rogers and Romanoff prepare to train new Avengers: Rhodes, Vision, Sam Wilson, and Wanda.