Vaas Montenegro is a character from Ubisoft's Far Cry video game franchise. He first appears as the secondary antagonist of the 2012 game Far Cry 3, and was extensively featured in promotional material for the game. Vaas is depicted as a capricious and mentally unstable character who antagonizes Far Cry 3's main character Jason Brody, and also serves as his dark psychological mirror. Vaas is later revealed to be a drug-addicted wayward member of the local community of the Rook Islands, the setting of Far Cry 3, who betrayed his people and aligned himself with the crime boss Hoyt Volker. Outside of Far Cry 3, Vaas' appearances include a live-action web series prequel called The Far Cry Experience, the virtual reality game Far Cry VR, and as the player character in Vaas: Insanity, a downloadable content (DLC) expansion for the 2021 game, Far Cry 6.

Conceived and designed by Ubisoft's development team as a villainous character who is comparable in stature to Star Wars's Darth Vader, Vaas is portrayed in all relevant media by Canadian actor Michael Mando. Mando decided to improvise for his audition and did not follow the developers' script, but they were so impressed by his performance that the character they had in mind was redesigned to match Mando's physicality. The game's story was eventually altered from the developers' initial intentions to accommodate a more frenetic, sociopathic villain in response to Mando's performance. The creative team worked in tandem with Mando to flesh out Vaas' characterization.

Vaas has been well received by the video game community and is often ranked on many lists of the best video game villains due to his depiction as an unhinged criminal. Mando's critically acclaimed performance was considered by many critics to be instrumental to the character's predominantly positive reception, and would influence the portrayal of villainous characters in subsequent sequels.

The lead writer of Far Cry 3, Jeffrey Yohalem, is credited as Vaas Montenegro's creator. For Far Cry 3, Yohalem took inspiration from public discourse about whether video games are good for the player's mental health, and about the concept of "gamification" in society as a whole. Yohalem wanted Vaas to represent a cautionary tale about what could potentially happen to player characters who found themselves caught up in their most indulgent, violent impulses; when interviewed by IGN about his thought process behind Vaas, Yohalem explained that video game developers always talk about 30-second loops, a line of thought within the video game industry which states that players should be put into a situation where what they are doing every 30 seconds is so satisfying that they never want to stop. Yohalem wanted to examine "what made games tick", and then examined the player's involvement in them and whether these experiences are enjoyable for the player, or whether they find themselves confronted by an "uncomfortable development", with this archetype represented by Vaas, a pirate who seems to be "on the knife edge between sanity and mental collapse". Yohalem opined that Vaas' monologue about the definition of insanity is in accord with the philosophies behind Far Cry 3's design, as it "perfectly encapsulates" the dark side of the concept of a gameplay loop which the writing team attempted to deconstruct.

Vaas was not part of the developers' original vision for Far Cry 3's major villains. He was meant to be a bald and muscular man named Bull, who looked similar to "a 300-pound, six-foot-tall bullmastiff dog". A second iteration of the character was named Pyro and had a heavily mutilated body. Michael Mando's audition and subsequent hiring prompted Ubisoft staff to alter their original plans for the character to accommodate Mando's likeness and mannerisms. Bull's physical fierceness transformed into Vaas' emotive and volatile personality, though such features were later downplayed as Mando's portrayal of Vaas enabled his personality to be expressed through subtle mannerisms to achieve the effect of a charming but menacing villain. Initially the character was called Lupo, but the name Vaas was picked once the graphic design was altered to incorporate Mando's appearance. This was done primarily because the developers faced difficulties matching Mando's facial musculature to the model.

Producer Dan Hay compared Vaas to Darth Vader, in that his presence is often short and brief, yet when he appears, he catches attention and galvanizes players' memories. Hay described Vaas as a character that was "very much in your face", which helped cement Jason's early status as a "victim". Yohalem added that Vaas' implied death at the game's midpoint was inspired by the novel To the Lighthouse, in which the protagonist dies midway through the story and the rest of the plot explores her absence.

Yohalem recalled that Vaas was a "lightning rod" with an "incredible gravity", and that the character become the subject of obsession in video game fandom before Far Cry 3 was even released. Yohalem concluded the critical and popular acclaim in response to Mando's performance as Vaas was a "lightning in a bottle" moment Ubisoft experienced for the first time with the character, and observed that the series would go on to explore the different possibilities of a dark central performance. Ubisoft staff originally considered creating a direct sequel to Far Cry 3 and entertained the idea of resurrecting Vaas, but abandoned it to commit to a standalone sequel with Far Cry 4.

To achieve their goal of creating nuanced characters, Ubisoft's development team made extensive use of performance and motion capture, so that actors could convey more complicated emotions on-screen. According to Anne Gibeault, associate producer for cinematics in the Montreal studio, a character's face and hands convey the most essential part of the animation process. Yohalem emphasized that the eyes are the most essential facial feature as they get noticed first, and that they make a character more emotionally resonant, and so players connect with the characters through eye contact. To perform his role as Vaas, Mando's gestures and facial expressions were translated into animation through carbon-fiber helmets, with cameras mounted about two feet from his face to record every squint, frown, or smile. Yohalem noted that actors have to “create a style between the exaggerated movements of the theatrical and the minimalism of film” for a motion capture performance.