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.

The sequel was announced in May 2012 after the successful release of The Avengers, with Whedon set to return as writer and director in August. Whedon 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 films 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).