The Saboteur is an open-world action adventure, set in Nazi-controlled Paris during Germany's rise to power in World War II. Players take the role of an unlikely hero: An Irish mechanic with nothing left to lose. Sean Devlin has lost all he loved in life because of the heartless Nazi occupation, and he now devotes his keen engineering skills to revenge, by destroying as much of the German army's equipment and infrastructure as he can. Considering his skills with explosives and heavy machinery -- and with his two fists, as well -- this is a significant amount of potential damage. The hero can run, climb, and make use of many different kinds of vehicles he finds. He is free to explore the 1930s City of Lights as the player wishes, and progress at his own pace down the paths he chooses, but contact with British intelligence operatives and members of the local underground resistance movement provides information that leads to more structured operations.

As he works toward his ultimate goal of vengeance against the high-ranking Nazi officer who ruined his life, Sean embarks on missions of sabotage, sniping, and assassination, using his mechanical skills, stealth, and street smarts. Each job presents unique goals and challenges, but in nearly all missions, the key is to remain unnoticed, using the element of surprise to take out an important Nazi officer or unleash massive damage on tanks and heavy artillery, and then slipping back into the shadows to fight again another day. The game represents Sean's subversive successes in a more indirect manner, as well, with its "Will to Fight" system. As the hero deals blow after blow to the occupying German forces, the repressed people of Paris are encouraged toward their own insurgency, and the streets and neighborhoods that Sean has freed from overbearing Nazi presence begin to take on a more colorful, positive appearance in the game, emboldening new allies and opening up more missions.