Honkai Impact 3rd (/ˈhɔːnˌkaɪ/, Chinese: 崩坏 3; pinyin: Bēnghuài 3; lit. 'Collapse 3rd', 'Deteriorate 3rd') is a 2016 free-to-play 3D science fantasy action role-playing game developed and published by miHoYo (with publishing outside mainland China under Cognosphere, trading as HoYoverse). It is the spiritual successor to Guns Girl Z, using many characters from the previous title in a separate story. The game is notable for incorporating a variety of genres, from hack and slash and social simulation, to elements of bullet hell, platforming, shoot 'em up and dungeon crawling across multiple single and multiplayer modes. It features gacha mechanics. It was first released on mobile devices and later ported to Microsoft Windows.

A massive expansion of the game, titled Honkai Impact 3rd Part 2 was released on February 29, 2024. Built upon the existing game, the update marks the start of the second major story arc of the game, with new characters, reworked UI, an updated engine, and a shift from a mission-based structure to a limited open-world structure.

In addition to the game, the storyline of Honkai Impact 3rd spans multiple supplementary media including a series of animated shorts, multiple manhua series, and promotional videos.

The word "Honkai", based on the Japanese word houkai (崩壊), is a direct translation of the Chinese 崩坏 (bēng huài) used in the original Chinese title. The "Impact" part of the title is absent from both the Chinese and Japanese versions, and is only used in English marketing.

In-game, the term 'Honkai Impact' (also 'Honkai Eruption' or 'Honkai Outbreak') refers to a large-scale Honkai disaster that coincides with the birth of a Herrscher.

Honkai Impact 3rd has players control a team of up to three characters, known as Valkyries, in real-time combat against various enemies. During battle, players may freely switch between characters and move around the battlefield. Each Valkyrie has unique attack, evasion, switch, and ultimate skills, as well as a type. The three main types: Mecha, Biologic, and Psychic, are based on a rock-paper-scissors-based system, wherein types are advantaged and disadvantaged depending on both the enemy type and their own type. The two additional types, Quantum and Imaginary, are disadvantaged over each other, neutral towards the above three types, and advantaged over themselves. A third additional type, Stardust, is advantaged towards itself and neutral to all other types. Valkyrie stats and skills can be changed with various weapons and equipment, which can be improved by using in-game resources. New equipment (known as Stigmata), weapons, and Valkyries can obtained either through in-game crafting or through a gacha system.

Single-player game modes include the Story campaign, consisting of stages punctuated by dialogue in cutscenes and full motion videos (FMVs); Chronicles, a series of brief side stories that explore Valkyries' backstories or other aspects of the world; and Open World, allowing exploration of several large open-ended fields to gather materials and complete various challenge tasks, coupled with their own storylines.

The game features various multiplayer cooperative and competitive modes, such as Memorial Arena, where players compete against a set of bosses for the highest score across the server; Abyss, where players attempt to progress as far as possible through a gauntlet of battles to compete for high scores against others in a small group, etc. Players are able to join groups of other players, called Armadas, which allow for more opportunities for events and rewards. Armadas allow for limited requesting of materials and resources from other players in the Armada.