Infinity Blade was an action role-playing game developed by Chair Entertainment and Epic Games and released through the Apple App Store on December 9, 2010. It was the first iOS video game to run on Unreal Engine 3. In the game, the unnamed player character fights a series of one-on-one battles in a derelict castle to face the immortal God King. When in battle, players swipe the screen to attack and parry, and tap the screen to dodge and block enemy attacks. Upon defeat, the player restarts the game as the character's descendant with the same items and experience level.

The game was developed by a team of twelve people, who took two months to make a playable demo and three more to finish the game. Infinity Blade was intended to demonstrate the new iOS version of the Unreal Engine, and to combine the combat of Karateka and Prince of Persia with the loneliness of Shadow of the Colossus. The game received four free expansions that added new equipment, endings, and game modes.

Infinity Blade was the fastest-grossing app in the history of iOS upon its release. It made US$1.6 million in its first four days, and over US$23 million by the end of 2011. It was well received by gaming critics. Reviews praised the graphics and compared the mobile game favorably to console games. Critics also praised the swipe-based combat system, but split opinions on the cyclical gameplay as either addictive or repetitive. Chair later released an arcade port and two sequels: Infinity Blade II and Infinity Blade III. Author Brandon Sanderson also wrote two novellas set between the games: Infinity Blade: Awakening and Infinity Blade: Redemption.

The game, along with its two sequels, was removed from the App Store on December 10, 2018, due to difficulties in updating the game for newer hardware.

In the primary portion of Infinity Blade, the player character travels a mostly linear path through a ruined castle and fights one-on-one battles with oversized enemies. The path through the castle is a series of discrete locations where the player can pan the camera around the stationary player character to view a fully three-dimensional area. The player taps locations highlighted onscreen to trigger either a short cutscene as the player character moves to the next location, or a sword battle with an enemy. During combat, the player controls the character's sword by swiping a finger across the screen. Players can touch icons at the bottom of the screen to dodge attacks by ducking right or left, or to block attacks with a shield, which has a limited number of uses during a single battle. Players may also parry incoming attacks with an intercepting sword move that, for example, parries an attack from the left with a swipe to the left. Each of these three counters can leave the enemy vulnerable to counterattack for a short period, but incorrect counters result in damage to the player character, as reflected in the health bar. When players fail in battle en route to the God King, the game resets to the location preceding the previous battle. Enemies can perform attacks that cannot be parried or blocked—such as a shield bash—that must be dodged. Players use two special abilities via icons atop the screen: the Super Attack temporarily stuns the opponent, and magic heals or attacks as indicated by drawing a given symbol. Both require time to recharge after use. When attacking, the player can swipe in any direction, and can do specific attack combinations to deal extra damage.

In addition to combat, there is also a mild role-playing component. An experience point system levels up the player character and their equipment (weapons, armor, shields, helms, and magic rings). Equipment pieces have special properties and a predetermined number of experience points required to master them. Mastering a piece of equipment increases its sale value but decreases the player's experience gain by 20%. Upon leveling up or mastering a piece of equipment, players gain attribute points that can be allotted towards four character attributes: health, attack, shield power, or magic. Each point can only be allocated once and is a permanent upgrade to the character. Players can purchase new equipment using in-game money from sacks and treasure chests found throughout the castle, defeated enemies, and sales of unused equipment. In-game money can be purchased with real money within the game.

The game follows a cyclical narrative structure in which the protagonist and his descendants individually explore a castle in a quest to battle the primary antagonist, the immortal God King. In the game's introduction, the non-playable protagonist has just finished this quest, but is slain by the God King. The player then assumes the role of the dead protagonist's descendant as he starts his journey at the beginning of the castle. This cycle, called a bloodline, continues after the player finally faces the God King and either dies or wins. The player may also choose to join the God King and terminate the cycle; upon doing so, the game resumes at the checkpoint before fighting the God King. Enemy difficulty increases with each bloodline cycle. Another bloodline ending is unlocked after purchasing the Infinity Blade item: the sword is placed into a pedestal in the castle's underground dungeons and three doors open. After then defeating each of the three "Deathless"—immortal beings like the God King—of increasing difficulty found within, a final fourth door opens, and the player faces a mechanized warrior guarding the high-tech chamber where the God King is reborn whenever he is killed. Upon defeating the mechanized warrior, the chamber is revealed to be controlled by an ancestor of the player character, who chose to serve the God King. After fighting the ancestor, the player character is told that the Infinity Blade can prevent immortals like the God King from resurrecting after death. The player is then given the option of either starting the next bloodline as they do when defeated, or resetting the game and starting New Game+ mode, which resets all gold and item progression but maintains the character's experience level, letting the player remaster the items and level up even further.

Chair Entertainment released four expansions as free updates to the game. The first, released December 20, 2010, added a new enemy, equipment, and microtransactions. It also removed an experience level cap. The second update, titled Infinity Blade: The Deathless Kings, was released on March 2, 2011, and added the dungeons as a second branch to the game's path. This expansion also added new equipment, enemies, and the second ending where the player character defeats his ancestor. The third update, Infinity Blade: Arena, was released on May 19, 2011. It added the player vs. player "Arena Mode", a tiered combat game progression where one player fights as the hero and the other as an enemy from the game. The update also included new equipment and a single-player version of Arena Mode called "Survival Mode". On October 4, 2011, a fourth update added a new enemy and new equipment to coincide with the announcement of the forthcoming sequel Infinity Blade II.