Splatoon 2: Octo Expansion

Splatoon 2: Octo Expansion is a 2018 downloadable content (DLC) expansion pack for the single-player mode of Splatoon 2, a 2017 third-person shooter video game for the Nintendo Switch. It was released on June 13, 2018. Set in an underground rapid transit system named the Deepsea Metro, the DLC follows an amnesiac Octoling, a humanoid octopus, nicknamed Agent 8. After becoming inadvertently trapped in the Metro alongside former military general Cap'n Cuttlefish, Agent 8 journeys through a multitude of testing facilities, at the direction of a talking telephone, with the goal of escaping to the surface.

The development of Octo Expansion began shortly after the release of Splatoon 2. Series producer Hisashi Nogami wanted to allow players to explore previously undeveloped aspects of Splatoon's world—especially those relating to the Octolings—through a story-driven, single-player adventure. The DLC's levels were designed to be more varied and challenging than those of Splatoon 2's regular story campaign. Octo Expansion's visual aesthetics took influence from the popular culture of eras such as the 1980s to elicit a mysterious atmosphere, while its dark, subterranean setting served to set itself apart from the series' colorful world.

Octo Expansion was met with positive reviews for its difficulty, unique artistic vision, and story that reviewers said expanded upon the narrative foundations of earlier Splatoon games. Numerous critics deemed it superior to Splatoon 2's regular single-player mode.