Aiden Pearce (also known as The Vigilante and The Fox) is a fictional character and the overarching protagonist of the Watch Dogs video game series developed by Ubisoft. He first appeared as the main protagonist of the original Watch Dogs (2014), in which he was portrayed by Noam Jenkins via performance capture. He also made a minor, non-speaking appearance in Watch Dogs 2 (2016), and returned as a playable character in Watch Dogs: Legion (2020), with Jenkins reprising his role. In Legion, Aiden serves as one of the two protagonists of the Bloodline expansion, alongside Wrench from Watch Dogs 2. The character has also appeared in media outside the games, such as the novels Watch Dogs //n/Dark Clouds (2014) by John Shirley, and Watch Dogs: Stars and Stripes (2022) by Sean Grigsby and Stewart Hotston.

In the franchise, Aiden is portrayed as a highly skilled grey hat hacker and vigilante based in Chicago, who utilizes the fictional ctOS system to manipulate the city's infrastructure and security features. After an attempt on his life results in the death of his young niece, Aiden embarks on a quest for revenge against those responsible, while slowly attempting to move on from his trauma. In Legion, which takes place nearly two decades after the events of Watch Dogs, Aiden relocates to London, where he tries to reconnect with his estranged nephew and becomes involved with the local hacking syndicate DedSec, which seeks to liberate the city from the control of an oppressive private military company.

Aiden was first revealed by Ubisoft at the E3 2012 conference in a demo trailer. According to director Jonathan Morin, Breaking Bad's main protagonist Walter White was a direct source of inspiration for Aiden, as they were both intentionally designed to be flawed antiheroes. Aiden's character has received a generally mixed reception, with many reviewers criticizing his perceived unlikability and lack of growth, although his appearance in the Bloodline expansion for Legion was met with more positive responses.

Aiden Pearce first appears as the protagonist of the original Watch Dogs game. His backstory establishes that he was born on 2 May 1974 in Belfast, Northern Ireland. At an unspecified point in time, he, along with his mother and younger sister Nicole Pearce, emigrated from Belfast to Chicago, where it is implied that his father was a criminal and an abusive parent. According to Aiden, he grew up in a rough neighborhood, where he was often engaged in violence and joined a gang, learning how to fight and use weapons. He later became proficient with computers and a skilled grey hat hacker, utilising Chicago's ctOS network to manipulate the city's infrastructure and security features. Operating as a fixer and thief, Aiden at some point met and befriended fellow hacker Damien Brenks, and the two formed a partnership.

In 2012, Aiden and Damien conduct a heist on the Merlaut Hotel, owned by Irish mob boss Dermont Quinn, in which they hack in and siphon money from people's bank accounts. However, Aiden abruptly ends the heist when he inadvertently triggers a silent alarm set by another hacker, giving himself and Damien away. On 26 October 2012, while Aiden is driving with his nephew Jackson and niece Lena to Pawnee, Illinois, Maurice Vega, a hitman hired by Quinn, shoots their car's tires, causing them to crash. While Aiden and Jackson survive, Lena dies in the crash, leading Aiden to vow revenge on those responsible.

A year later, Aiden tracks down and interrogates Vega, but is unsuccessful in learning the identity of his contractor. Leaving Vega in the hands of his partner, hired fixer Jordi Chin, Aiden goes to visit Nicole and Jackson for the latter's birthday. Having grown apart from his relatives due to the tragedy of Lena's death and his obsession with tracking down the perpetrators, Aiden makes an attempt to reconnect with Nicole and Jackson, only to learn that someone has been harassing them. With the help of Clara Lille, a member of the hacking syndicate DedSec, Aiden discovers the harasser was hired by Damien, who sought to gain his attention so that Aiden would help him find the other hacker from the failed Merlaut job. When Aiden refuses, Damien kidnaps Nicole to force him to comply.

After setting up a new hideout, Aiden works with Clara to track down the hacker, leading them to gang leader and Army veteran Delford "Iraq" Wade. Following a failed first attempt to breach Iraq's servers by blackmailing his cousin Tyrone "Bedbug" Hayes, Aiden nonetheless manages to obtain a data sample revealing that Iraq has information on almost every citizen of Chicago, which allows him to protect his gang from the authorities. As the recovered data is encrypted beyond Aiden and Clara's abilities, the pair decide to track down legendary hacker and former Blume whistleblower Raymond "T-Bone" Kenney. Aiden finds Kenney and erases his identity from ctOS to allow him to return to Chicago, before protecting him from Blume's private security forces, who were tipped off to Kenney's location by Damien in exchange for full access to ctOS. Upon returning to Chicago, Aiden assaults Iraq's compound to finish downloading its server data, and kills Iraq when the latter confronts him.

Aiden, Kenney, and Clara are unable to decrypt Iraq's data because another hacker, JB "Defalt" Markowicz, infiltrates their system and steals it. Defalt also reveals that Clara was hired to track down Aiden after the Merlaut job, therefore being indirectly responsible for Lena's death. Aiden angrily dimsisses Clara, and sets up a meeting with Damien, who demands the data he recovered from Iraq. When Aiden lies about being in possession of the data, Damien calls his bluff and exposes his identity to the authorities. After retrieving the stolen data from Defalt, Aiden track down Nicole with Kenney's help and rescues her, then bids her and Jackson farewell as the two leave Chicago for their safety.