- Thor (Rejoins)
- Hulk (Dr. Bruce Banner) (Rejoins)
- Iron Man (Tony Stark)
- Spider-Man (Peter Parker) (Joins team) (Death)
- Vision (Death)
- Wanda Maximoff (Rejoins) (Death)
- Steve Rogers (Rejoins)
- Falcon (Sam Wilson) (Rejoins) (Death)
- Black Widow (Natasha Romanoff) (Rejoins)
- War Machine (Col. James "Rhodey" Rhodes)
- Masters of the Mystic Arts
- Guardians of the Galaxy (Disbands)
- Black Panther (King T'Challa) (Death)
- Dora Milaje
- White Wolf (Bucky Barnes) (Death)
- Eitri (First appearance)
- Princess Shuri (Death off-screen)
- Jabari Tribe
- Numerous unnamed members
- Border Tribe
- Numerous unnamed members
- Thanos (Main story and flashback)
- Black Order (Real name first revealed) (Disbands)
- Heimdall (Death)
- Loki (Death)
- Pepper Potts
- Uncle Morgan (Mentioned)
- Adolf Hitler (Mentioned)
- The Beatles (Mentioned)
- F.R.I.D.A.Y. (Voice)
- Midtown School of Science & Technology Students
- Stan Lee (Last appearance)
- Squidward (Mentioned)
- Odin (Mentioned)
- Hela (Mentioned)
- Ego (Mentioned)
- Meredith Quill (Mentioned)
- Kevin Bacon (Mentioned)
- Gamora's mother (Only in flashback) (Apparent death)
- Ovette (Mentioned)
- Kamaria (Mentioned)
- The Collector (Taneleer Tivan) (Illusion)
- Secretary Thaddeus "Thunderbolt" Ross (Appears on a computer screen, TV, or hologram only)
- Hawkeye (Clint Barton) (Mentioned)
- Ant-Man (Scott Lang) (Mentioned)
- J.A.R.V.I.S. (Mentioned)
- Ultron (Mentioned)
- Frigga (Mentioned)
- Malekith (Mentioned)
- Jesus (Mentioned)
- Flash Gordon (Mentioned)
- Red Skull / Stonekeeper (Johann Schmidt) (Revealed to be alive)
- A'Lars (Mentioned)
- Nick Fury (Death)
- Maria Hill (Death)
- Cameron Klein (Mentioned)
Races and Species:
- Titanians (Main story and flashback)
- Human-Celestial Hybrids
- Flora colossi
- Zehoberei (Main story and flashback)
- Cotati (Mentioned)
- Dark Elves (Mentioned)
- Chitauri (Main story and flashback)
- Leviathans (Only in flashback)
- Dwarves of Nidavellir
- Earth-199999 (Main story and flashback)
- United States
- United Kingdom
- Zen-Whoberi (First appearance) (Only in flashback)
- Nidavellir (First full appearance)
- Furnaces of Nidavellir (First appearance)
- Xandar (Mentioned)
- Collector's Museum (Destruction)
- Vormir (First appearance)
- Asgard (Mentioned)
- Jotunheim (Mentioned)
- Contraxia (Mentioned)
- Hel (Mentioned)
- Mirror Dimension
- Soulworld (First appearance)
- The Garden / Planet 0259-S (First appearance) (Unnamed)
- Infinity Gauntlet
- Infinity Stones (Last appearance)
- Proxima Midnight's Spear (First appearance)
- Corvus Glaive's Glaive (First appearance)
- Cull Obsidian's Hammer (First appearance)
- Tesseract (Destroyed)
- Cloak of Levitation
- Eye of Agamotto (Destroyed)
- Sling Ring
- Cauldron of the Cosmos (First appearance)
- Winds of Watoomb (First appearance)
- Sokovia Accords (Mentioned)
- Shield of the Seraphim
- Tony Stark's Sunglasses
- Spider-Man's Suit
- Arc Reactor
- Iron Man Armor MK L (First full appearance)
- Iron Spider Armor
- Star-Lord's Microsoft Zune (Behind the scenes)
- Translator Implant
- Gamora's Swords (Destroyed)
- Drax's Knives
- Star-Lord's Helmet
- Quad Blaster
- Captain America's Uniform
- Exo-7 Falcon Flight Harness
- Black Widow's Batons
- War Machine Armor MK IV (First appearance)
- Panther Habit
- M'Baku's War Club
- White Wolf's Bionic Arm (First appearance)
- Space Throne
- Crimson Bands of Cyttorak (First appearance)
- Images of Ikonn (First appearance)
- Steve Rogers' Wakandan Vambrace Shields (First appearance)
- Stormbreaker (First appearance)
- Mjolnir (Mentioned)
- Hulkbuster Armor 2.0 (First appearance)
- Kimoyo Beads
- Vibranium Strike Gauntlets
- Captain Marvel's Suit (First appearance; on-screen)
- The Statesman (Destroyed)
- The Commodore (Destroyed)
- Sanctuary II
- Benatar (First appearance)
- Q-Ship (First appearance)
- Dragon Flyers (Cameo)
- Necrocraft (Destroyed)
Having acquired the Power Stone, one of the six Infinity Stones, from the planet Xandar, Thanos and his lieutenants—Ebony Maw, Cull Obsidian, Proxima Midnight, and Corvus Glaive—intercept a spaceship carrying the surviving Asgardians. As they extract the Space Stone from the Tesseract, Thanos subdues Thor, overpowers Hulk, and kills Loki. Heimdall sends Hulk to Earth using the Bifröst before being killed. Thanos departs with his lieutenants and obliterates the ship.
Hulk crash-lands at the Sanctum Sanctorum in New York City, reverting to Bruce Banner. He warns Stephen Strange and Wong about Thanos' plan to kill half of all life in the universe; in response, Strange recruits Tony Stark. Maw and Obsidian arrive to retrieve the Time Stone from Strange, drawing the attention of Peter Parker. Maw captures Strange, but fails to take the Time Stone due to an enchantment. Stark and Parker pursue Maw's spaceship, Banner contacts Steve Rogers, and Wong stays behind to guard the Sanctum.
In Edinburgh, Midnight and Glaive ambush Wanda Maximoff and Vision in order to retrieve the Mind Stone in Vision's forehead. Rogers, Natasha Romanoff, and Sam Wilson rescue them and take shelter with James Rhodes and Banner at the Avengers Facility. Vision offers to sacrifice himself by having Maximoff destroy the Mind Stone to keep Thanos from retrieving it. Rogers suggests they travel to Wakanda, which he believes has the resources to remove the stone without destroying Vision.
The Guardians of the Galaxy respond to a distress call from the Asgardian ship and rescue Thor, who surmises Thanos seeks the Reality Stone, which is in the possession of the Collector on Knowhere. Rocket and Groot accompany Thor to Nidavellir, where they and Eitri create Stormbreaker, a battle-axe capable of killing Thanos. On Knowhere, Peter Quill, Gamora, Drax, and Mantis find Thanos with the Reality Stone already in his possession. Thanos kidnaps Gamora, his adopted daughter, who reveals the location of the Soul Stone to save her captive adopted sister Nebula from torture. Thanos and Gamora travel to Vormir, where Red Skull, keeper of the Soul Stone, informs him the stone can only be retrieved by sacrificing someone he loves. Thanos reluctantly kills Gamora, earning the stone.
Nebula escapes captivity and asks the remaining Guardians to meet her on Thanos' destroyed homeworld, Titan. Stark and Parker kill Maw and rescue Strange. Landing on Titan, they meet Quill, Drax, and Mantis. The group forms a plan to remove Thanos' Infinity Gauntlet after Strange uses the Time Stone to view millions of possible futures, seeing only one in which Thanos loses. Thanos arrives, justifying his plans as necessary to ensure the survival of a universe threatened by overpopulation. The group subdues him until Nebula deduces that Thanos has killed Gamora. Enraged, Quill attacks him, allowing Thanos to break the group's hold and overpower them. Stark is seriously wounded by Thanos, but is spared after Strange surrenders the Time Stone to Thanos.
In Wakanda, Rogers reunites with Bucky Barnes before Thanos' army invades. The Avengers, alongside T'Challa and the Wakandan forces, mount a defense while Shuri works to extract the Mind Stone from Vision. Banner, unable to transform into the Hulk, fights in Stark's Hulkbuster armor. Thor, Rocket, and Groot arrive to reinforce the Avengers; Midnight, Obsidian, and Glaive are killed and their army is routed. Thanos arrives and despite Maximoff's attempt to destroy the Mind Stone, removes it from Vision's head, killing him.
Thor severely wounds Thanos, but Thanos activates the completed Infinity Gauntlet and teleports away. Half of all life across the universe disintegrates, including Barnes, T'Challa, Groot, Maximoff, Wilson, Mantis, Drax, Quill, Strange, and Parker, as well as Maria Hill and Nick Fury, although Fury is able to transmit a signal to Carol Danvers first. Stark and Nebula remain on Titan while Banner, M'Baku, Okoye, Rhodes, Rocket, Rogers, Romanoff, and Thor are left on the Wakandan battlefield. Meanwhile, Thanos watches a sunrise on another planet.
Additionally, Stan Lee makes a cameo as a school bus driver. Winston Duke and Florence Kasumba reprise their roles as M'Baku and Ayo, from Black Panther, respectively. Kerry Condon voices F.R.I.D.A.Y. Jacob Batalon, Tiffany Espensen, Isabella Amara, and Ethan Dizon reprise their roles as Ned Leeds, Cindy Moon, Sally Avril, and Tiny McKeever, from Spider-Man: Homecoming, respectively. Ross Marquand takes over the role of Red Skull, who was portrayed by Hugo Weaving in Captain America: The First Avenger. Ameenah Kaplan portrays Gamora's mother. Michael Anthony Rogers and co-writer Stephen McFeely make cameos as Ross' aides. Samuel L. Jackson and Cobie Smulders make uncredited appearances in the post-credits scene as Nick Fury and Maria Hill, respectively. One of the deleted scenes featured Jon Favreau reprising his role as Happy Hogan, along with co-director Joe Russo making a cameo appearance as a paparazzi photographer.
- This film was announced during Marvel Studios' event at El Capitan Theatre on October 28, 2014.
- Although Avengers: Infinity War - Part I was this film's original title, the Russo brothers subsequently confirmed that this film and Part II would be retitled to emphasize the differences between the two films. The first part became simply Avengers: Infinity War, while the second part had yet to be retitled. The second part's new title was revealed to be Avengers: Endgame on December 7, 2018 with the release of its first trailer.
- Filming for this film and Avengers: Endgame started on January 23, 2017, and wrapped on July 14, 2017 for the former.
- About two months before this film was set to release, its American premiere date was moved up one week, from May 4 to April 27, coinciding with its worldwide release.
- For this film, Black Order member Black Dwarf was adapted with the name "Cull Obsidian." In the comics, "Cull Obsidian" is an alternative name for the Black Order.
- The official poster for this film contains two visual errors in it. The first is Thor's scar being over the wrong eye (left instead of right), and the second is Bucky's bionic arm not being fully transposed over his left arm (on the wrist).
- This film broke both the domestic opening weekend box office record and worldwide opening record with a $250 million domestic gross and $630 million worldwide, beating the records set by Star Wars: The Force Awakens ($247.9 million) and Fate of the Furious ($541.9 million), respectively.
- Additionally, this film broke the record for the fastest time a film managed to reach $1 billion at the worldwide box office, on its 11th day of release, again beating Star Wars: The Force Awakens which did so on its 12th day.
- This film became the 4th film in history to earn $2 billion in its worldwide box office gross, alongside Star Wars: The Force Awakens, Titanic, and Avatar.
- With a worldwide total box office gross of $2 billion, this film became the highest-grossing film of 2018, and at its peak the 4th-highest-grossing film of all time.
- The release date of this film was around the time of the 10th Anniversary of the Marvel Cinematic Universe, which first appeared in Iron Man.
- With a running time of 2 hours and 29 minutes, this was, at the time of its release, the longest Marvel film.
- Writers Christopher Markus and Stephen McFeely toyed with the idea of introducing Richard Rider as the only surviving member of the Nova Corps who would herald Thanos' arrival instead of the Hulk.
- An initial draft for this film included a reunion between Iron Man and Captain America. According to Stephen McFeely, the scene was scrapped because it meant slowing down the aspect of Thanos from the film.
- An early draft for this film had Falcon go to space instead of Spider-Man.
- In this film's French dub, Tony Stark insults Ebony Maw by calling him Voldemort, instead of Squidward.
- The Russo Brothers wanted Steve Rogers' phone number (678-136-7092) to work in real life and redirect to a fake voicemail from the character. They couldn't do it because of the intervention of the film's affiliated legal department.
- A scrapped idea for the rescue of Doctor Strange from Ebony Maw had Tony send his Iron Man Armor MK L onto Strange to protect him, with the armor forming itself around the Eye of Agamotto and using it as its power source. In turn, Tony would have donned the Cloak of Levitation. The idea behind this concept was to switch the heroes' power sets to explore new interactions between the characters.
- War Machine was originally going to wear two suits in this movie. This ultimately got narrowed down to one armor, which combined the best elements of the two into one.
- An early idea for Thor's journey took inspiration from the character's mythical roots, having him fight the Midgard Serpent to obtain Stormbreaker. According to McFeely, the initial approaches to Thor's mission were "much too adventure-related, and insufficiently character-based."
- The original script for this film had Star-Lord fail to bring himself to try to kill Gamora. The scene was revisited after receiving input from Star-Lord's actor Chris Pratt and Guardians of the Galaxy director James Gunn.
- Drax's line asking, "Why is Gamora?" during the stand-off between Iron Man and Star-Lord was brought up by his actor, Dave Bautista, himself.
- In an early version of the movie's plot, Bruce Banner would have evolved into "Smart Hulk" during the battle in Wakanda. Before merging, Banner and Hulk would have had a confrontation in a metaphysical mindscape taking the form of the gladiator arena from Thor: Ragnarok. After this encounter, the two characters would have come out merged. The fusion would have taken place during Banner's confrontation against Cull Obsidian, with the merged Hulk busting out of the Hulkbuster 2.0. This plot resolution was scrapped late into development, which caused scenes from the first act of Avengers: Endgame to be reshot since they made use of Smart Hulk.
- An earlier draft of the movie saw Doctor Strange pushing Thanos through time and space in a surreal sequence to have him judged by the Living Tribunal. According to Markus, the idea was scrapped because, "We were in the middle of a really fast-paced fight, so to stop it for an LSD trip kind of sucked the air out of it."
- According to James Gunn, Groot's final words before dying meant "Dad." Co-director Anthony Russo has confirmed the script did include what Groot's final words meant.
- The final moments of Spider-Man's death scene were improvised by Tom Holland, namely the repeated blubbering of the line, "I don't want to go."
- In an earlier draft for this film and its sequel, Thanos snapping his fingers didn't happen until the second film. This was changed because "it would feel more like a cliffhanger than we intended" according to co-writer Christopher Markus.
- The Russo Brothers confirmed that characters like Betty Ross and Lady Sif died off-screen due to Thanos' finger snap, while others such as Howard the Duck, Aunt May and Nakia survived. They refused to confirm the status of some characters because the information was deemed to be "too spoilery." These characters include Jane Foster, Ned Leeds, Shuri, Korg and Miek. Avengers: Endgame would later reveal that Ned Leeds and Shuri were snapped, while Korg and Miek survived. Jane Foster's status remained unknown, and while the Russos confirmed Aunt May to have survived, Spider-Man: Far From Home establishes she did not.