Avengers: Infinity War Screenplay

Principal photography began on January 23, 2017, under the working title Mary Lou, at Pinewood Atlanta Studios in Fayette County, Georgia, with Trent Opaloch as director of photography. Infinity War, along with its sequel, were shot using IMAX/Arri 2D cameras, thus marking the first time that a Hollywood feature film was shot entirely with IMAX digital cameras. In early February, Marvel confirmed the involvement of Robert Downey Jr. as Tony Stark / Iron Man, Chris Pratt as Peter Quill / Star-Lord, and Tom Holland as Peter Parker / Spider-Man in the film. Additional filming took place in Scotland beginning in February 2017. The filming occurred in Edinburgh, Glasgow and the Scottish Highlands, with studio work taking place at Wardpark Studios in Cumbernauld. Filming also began at Durham Cathedral in Durham, England in early May 2017. In late June 2017, filming occurred in Downtown Atlanta, as well as Atlanta's Central Park in early July, before moving to Queens, New York in the middle of the month. Filming concluded on July 14, 2017. For the film's final scene, where Thanos emerges healed in a nipa hut, the filmmakers partnered with Indochina Productions, a studio based in Thailand, to acquire footage of the Banaue Rice Terraces at Ifugao, Philippines.

Later in July 2017, Joe Russo stated there were a couple of unfinished scenes for Infinity War that would be shot "in the next few months". In early March 2018, Disney moved the release of Infinity War in the United States to April 27, 2018, to have it be released the same weekend as some of its international markets. With an estimated budget in the range of $316–400 million, it is one of the most expensive films ever made.

Avengers: Infinity War held its world premiere at the Dolby Theatre in Los Angeles on April 23, 2018, screening also at the adjacent El Captian Theatre and Grauman's Chinese Theatre. It was released in most countries worldwide, including the United States, on April 27, 2018, with a few debuts beginning as early as April 25, and was shown in IMAX and 3D on select screens. In the United States, the film opened in 4,474 theaters, 408 of which were IMAX; this was the widest release for a Disney title ever and the second-widest ever after Despicable Me 3's 4,529 theaters. Three of AMC Theaters' locations screened the film for 24 hours straight, with 53 of their locations having showtimes at either 2 am or 3 am to accommodate demand. In India, the film had the biggest release ever for a Hollywood film, opening on nearly 2,000 screens in four languages. The film also screened in 515 4DX theaters in 59 countries. It was originally scheduled to be released on May 4, 2018 in the United States. The Chinese release of the film, which opened on May 11, 2018, was originally scheduled to end on June 10, 2018, but was granted a "rare" extension of 30 days, to end on July 9, 2018.

Select footage from the film was screened around various cities during the film's press tour in early April, ahead of the film's Los Angeles premiere. The Russos noted that only a limited amount of the film would be shown at these screenings to reduce the chance of spoilers being leaked. Adam Chitwood of Collider commented that this was "highly unusual as most Marvel movies are screened in their entirety for press about a month before they hit theaters". Ahead of the United States release, AMC Theaters in New York City and Orlando, Florida aired an eleven-MCU film marathon beginning on April 25, leading to a screening of Infinity War. The El Capitan Theater in Los Angeles also had a similar marathon ahead of the film's release.