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.

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.

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.

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.

Having killed Strucker, he recruits the Maximoffs, who hold Stark responsible for their parents' deaths by his company's weapons and goes to the base of arms dealer Ulysses Klaue in Johannesburg to get vibranium.

The Avengers attack Ultron and the Maximoffs, but Wanda subdues them with haunting visions, causing Banner to turn into the Hulk and rampage until Stark stops him with his anti-Hulk armor.

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.

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 skyward, intending to crash it into the ground to cause global extinction.

Pietro dies when he shields Barton from gunfire, and a vengeful Wanda abandons her post to destroy Ultron's primary body, which allows one of his drones to activate the machine.

Later, with the Avengers having established a new base run by Fury, Hill, Cho, and Selvig, Thor returns to Asgard to learn more about the forces he suspects have manipulated recent events.

[88] In March 2012, Joss Whedon, director of the first film, stated that he would want a sequel to be more small, personal, and painful; that is "not just a rehash of what seemed to work the first time", and with a theme full of originality to itself.

[89] Despite the production of the film becoming increasingly wider in scope, Feige maintained that this was not their intention, always looking to see where the team wanted to take the characters, over how to make it bigger than The Avengers.

[100] Feige revealed that Captain Marvel, who starred in her own MCU film in 2019, appeared in an early draft of the screenplay, but was removed since the character had not yet been cast, saying, "It didn't feel like the time.

"[101] Whedon went so far as to shoot visual effects plates for Captain Marvel to fly into Avengers Headquarters at the end of the film; those shots were reused; however, for Scarlet Witch instead.

[39] Whedon relished at the storytelling opportunities by introducing a character with telepathic powers, explaining, "it meant we could spend a little time inside the Avengers' heads—either their past or their impressions of what's going on, or their fears, or all of the above.

[124][126] Second unit crews shot action sequences without the main cast, to be used as background plates for scenes featuring the Hulk, in the Central Business District of Johannesburg for a period of two weeks.

[150] Following the completion of principal photography several more cast members were revealed including Stellan Skarsgård,[61] Anthony Mackie,[53] Idris Elba, and Tom Hiddleston, reprising their roles from previous MCU films.

Method also contributed to Iron Man's new Mark 45 suit and played a key role in creating Scarlet Witch's CG mind control effect.

He replaced Alan Silvestri, who composed the score for the first film, and Tyler's hiring marked his third collaboration with Marvel following Iron Man 3 and Thor: The Dark World in 2013.

[170][171] On March 18, 2014, ABC aired a one-hour television special titled, Marvel Studios: Assembling a Universe, which included a sneak peek of Avengers: Age of Ultron.

[186] In November 2014, ABC aired another one-hour television special titled Marvel 75 Years: From Pulp to Pop!, which featured behind the scenes footage of Age of Ultron.

[190] The episodes "The Frenemy of My Enemy" and "The Dirty Half Dozen" feature "Easter eggs, plot threads and other connective tissue leading into the opening scene of Avengers: Age of Ultron" while "Scars" explores the aftermath of the film.

[203] On April 27, Downey and Renner along with executives from Marvel Entertainment rang the opening bell of the New York Stock Exchange in celebration of the film's theatrical release.

[223] In July 2015, Whedon stated that he did not intend on releasing a director's cut of Avengers: Age of Ultron because despite the film's complexity, he was satisfied with the theatrical version and did not think it needed to be tweaked.

[231] Deadline Hollywood calculated the film's net profit as $382.32 million, accounting for production budgets, marketing, talent participations, and other costs; box office grosses and home media revenues placed it fourth on their list of 2015's "Most Valuable Blockbusters".

[215][243] It held the record for advance-ticket sales rate, accounting for 96% of tickets reserved, breaking Transformers: Dark of the Moon's (2011) record of 94.6% in 2011, the widest release ever, across 1,826 screens, also breaking Dark of the Moon's 1,420 screens, and the fastest imported film to surpass one million admissions, doing so in two days;[245] it topped the box office for three consecutive weekends,[246] and became the biggest Disney/Marvel release as well as the second-biggest Western film in the country.

The website's critical consensus reads, "Exuberant and eye-popping, Avengers: Age of Ultron serves as an overstuffed but mostly satisfying sequel, reuniting its predecessor's unwieldy cast with a few new additions and a worthy foe.

[254] Todd McCarthy of The Hollywood Reporter said, "Avengers: Age of Ultron succeeds in the top priority of creating a worthy opponent for its superheroes and giving the latter a few new things to do, but this time the action scenes don't always measure up.

"[259] Helen O'Hara of Empire praised the interactions between the characters, the action set-pieces and Whedon's ability as a director in her review, stating that the film "redefines the scale we can expect from our superheroes.