Dishonored is a first-person stealth and action game with elements of role-playing. It is set in the fictional industrial city of Dunwall in 1666, modeled after the London of the Victorian era, but mixed with a futuristic vision with magical and steampunk elements. Players take the role of Corvo Attano, Royal Protector of the Empress Jessamine Kaldwin, who is framed for murder and the abduction of Emily, the daughter of the empress. This leads him to seek revenge and assassinate those who conspired against him. The game consists of a series of assassination missions that can be completed through pure violence, pure stealth, or a mix of both. Corvo has access to various weapons, supplemented with magical abilities by the being The Outsider. Each mission offers various non-linear approaches and many of these are found by exploring the environment. With special attention to stealth, it is possible to complete the game in a non-lethal manner.

Large parts of the game are spent exploring with a focus on verticality, so Corvo can jump, slide, sneak, sprint, lean, mantle and swim. Melee attacks are performed through the right hand, with various weapons used to stab, slash, block and parry. Staying undetected with stealth kills fills up an adrenaline gauge that makes combat more effective. On the other hand, brutal and open attacks trigger a chaos system that causes more patrols to appear, rats swarm the environment and NPCs can even start attacking each other, disrupting all serenity in the game and the characters' actions. This also affects conversations and quests. Certain side missions can lower the chaos setting, but it can be avoided altogether by hiding bodies or preventing alarms from being activated. Stealth skills include aerial attacks, slitting throats, sleeper holds and tranquilizer darts for rendering a character unconscious. The stealth system is based on occlusion; hiding behind objects and staying out of the field of vision. The lighting is of lesser importance. Stealth can also be used to eavesdrop on conversations and gain information about characters and their motives before planning a route of attack. Corvo can be revealed through sound, but he can also use it to his advantage to lure away others. Guards have various stages of awareness that influence their responses.

Ranged weapons and magic are used through the left hand. There are pistols and crossbows with various types of ammunition, as well as gadgets such as razor mines, smoke bombs and grenades. Coins can be collected to upgrade weapons and gadgets. Players also discover blueprints that provide access to advancement equip upgrades, forged at Piero's workshop. Magic is provided through six active and four passive abilities. The active ones include blink to teleport short distances, dark vision to improve vision, devouring swarm to summon rats, healing, possession (both humans and animals), time bend to stop time, and windblast to create a gust of wind. Runes need to be discovered and collected to unlock and enhance these powers. The passive ones are vitality for additional health, blood thirsty to build up adrenaline by blocking attacks for a much stronger counter, agility for more speed and longer jumps, and shadow kill that turns enemies to dust when they are killed. Magic drains mana and it takes a certain amount of time to have it regenerate. There are also about 40 bone charms to be discovered that provide additional perks, but only three can be active at a single moment and they cannot all be unlocked in a single playthrough.

Between missions, Corvo returns to The Hound Pits, a drinking establishment that acts as a hub between missions. Dunwall is the capital city of the Empire of Isles, a collection of our nations. There is much water in the surroundings and to the east of the sea is Pandyssian Continent, a giant land mass. The background story describes Dunwall as a hub for fishing and whaling, as whale oil has become a major power source. At the same time the city is burdened by a plague, spread through dogs and rats, that divides the rich from the poor in districts through energy beams known as Walls of Light. These evaporate anyone passing through, except for the city watch, but can be deactivated by removing the energy source or through other means. Other elements and items include arc pylons that disintegrate anyone close, elixirs to refill health and mana, food, and single-use rewire tools to hack city devices. Infected are known as Weepers. They cry blood and exhibit a lot of violence. The city watch consists of Tallboys, mechanized officers of long legs. Corvo initially gets to escape through the Loyalists, a group of activists that plans to overthrow the government. The player's approach, especially in regard to killing, determines the game's ending.