Metroidvania is a sub-genre of action-adventure games focused on nonlinear exploration and guided progression with a need to acquire key items to enter certain areas. The term is a portmanteau of the names of the video game series Metroid and Castlevania, based on the template from Metroid (1986), Castlevania II: Simon's Quest (1987), Super Metroid (1994), and Castlevania: Symphony of the Night (1997).

These games usually feature a large interconnected world map the player can explore, although parts of the world will be inaccessible to the player until they acquire special items, tools, weapons, abilities, or knowledge within the game. Acquiring such improvements can also aid the player in defeating more difficult enemies and locating shortcuts and secret areas, and often includes retracing one's steps across the map. Through this, Metroidvania games include tighter integration of story and level design, careful design of levels and character controls to encourage exploration and experimentation, and a means for the player to become more invested in their player character through role-playing game elements. While early examples were usually two-dimensional side-scrolling platform games, the term has since been applied to top-down and 3D games.

The first Metroid game in 1986 established principles of the non-linear platformer that were refined through multiple iterations, with Super Metroid in 1994 considered to have polished the style of gameplay core to Metroidvanias. Castlevania: Symphony of the Night in 1997 is considered the defining Metroidvania game, incorporating role-playing elements from the Legend of Zelda series with non-linear traversal within the Castlevania series; most subsequent Castlevania games followed its approach and refined the genre. Symphony of the Night's assistant director, Koji Igarashi, is credited with establishing key principles of Metroidvanias through his work on other Castlevania games. In the 2010s, a resurgence in Metroidvanias came about due to several critically praised independently developed games.

While not the first game of its kind (for example, Below the Root was released in 1984, or Brain Breaker in 1985), Metroid (1986, Nintendo Entertainment System) is generally considered the most influential game for the Metroidvania genre. Nintendo's goal for the title was to create a non-linear adventure game to set it apart from other games at the time, requiring the player to retrace their steps while providing permanent power-ups in contrast to how other adventure games only offered power-ups with temporary effects. The series was popular, and future titles refined the exploration approach while adding more story elements to the title such as with Super Metroid (1994, Super Nintendo Entertainment System). Super Metroid refined several aspects from the previous Metroid games, including a diverse array of locations and adding many secrets for players to find; these secrets also enabled players to find ways to break the expected sequence that the designers had envisioned players would approach the game, making it a popular title among speedrunners.

During this time, the gothic horror-themed platformer series Castlevania was gaining popularity. The original Castlevania (1986, NES) featured discrete levels that the player completed in a sequential manner. It was followed by Vampire Killer (1986, MSX) and Castlevania II: Simon's Quest (1987, NES) which experimented with non-linear adventure gameplay, before the series returned to the more linear style of the original Castlevania. Series lead Koji Igarashi found that as they continued to produce sequels to cater to fans of the series, experienced players would race through the levels, while new players to the series would struggle with some stages. To try to make a title that would be more widely appreciated across play levels and extend the gameplay time of the title, Igarashi and others on his team looked toward the ideas used by The Legend of Zelda series into the development of Castlevania: Symphony of the Night (1997, PlayStation). With Symphony of the Night, Igarashi introduced new concepts into the Castlevania series from Zelda such as a large open world to explore and the need to acquire key items to enter certain areas, elements already present in non-linear platformers like Super Metroid. However, Symphony of the Night distinguished itself from prior non-linear platformers via the incorporation of console role-playing game elements with the means for the player to improve their character's attributes through an experience system. The changes for Symphony of the Night proved popular with players, and most subsequent games in the series would follow this formula. With the releases of Super Metroid and Castlevania: Symphony of the Night, the formula these games presented would form the foundations of what are considered Metroidvanias today. Castlevania: Symphony of the Night had also become a critical and financial success over time, establishing that there was a desire by players for Metroidvania-style games. As this neologism started to be adopted, Igarashi stated that Symphony of the Night was more inspired by Zelda, not Metroid, although he stated that Metroidvania "fits very well". Other figures in the game industry have since used Zeldavania interchangeably, with the Zelda series recognized as following the same formula.

The concept of Metroidvanias started to gain more attraction when other parties began to develop games in the same style. Cave Story (2004, Microsoft Windows) was developed by Daisuke Amaya as an homage to Metroid and other classic games; the game was critically praised showing the scope of what one person could do, and highlighted another take on the Castlevania and Metroid games, as well as vitalizing the 2D platformer genre as a viable indie game format. Shadow Complex (2009, Xbox 360) by Chair Entertainment was developed based on the premise that Super Metroid was "the pinnacle of 2D game design". The game received highly positive reviews, and remains one of the best-selling downloadable titles on the Xbox 360 service. Due to games like these, the Metroidvania genre began to take off in both publisher-driven and independent games development. Drinkbox Studios' Guacamelee! (2013), Moon Studios' Ori and the Blind Forest (2015), and Team Cherry's Hollow Knight (2017) are examples of modern indie Metroidvanias that have reached critical acclaim. The genre's indie renaissance did not go unnoticed by Igarashi. In May 2015, he released a Kickstarter campaign for Castlevania-influenced Bloodstained: Ritual of the Night (2019), which was the highest-funded video game on Kickstarter at the time.

While the word "Metroidvania" is commonly used presently to describe games in this genre, or games that have elements of this genre, the origins of the term are unclear; Igarashi notes that he did not coin the phrase, though is grateful for the invention of the term. Igarashi noted that with Symphony of the Night the goal was to have exploration closer to the top-down Zelda approach, but with the side-scrolling nature, it was compared more to Metroid, and believes this is how the portmanteau came about. A similar portmanteau "Castleroid" is sometimes used as well for describing this genre. Video game journalist Jeremy Parish, who manages the Metroidvania.com site that has attempted to catalog all known Metroidvania games, acknowledges he helped to popularize the term but had learned it from his former co-worker at 1UP.com, Scott Sharkey, who had used the term to describe the games in the Castlevania series that had adopted some elements from the Metroid series. Japanese gaming publication Famitsu wrote in 2020 that the term for the exploration-based action game genre "Metroidvania" had only recently become a commonly used term in Japan recently.

The term 'Metroidvania' is most often used to refer to a platforming game that features a single large, interconnected map, generally with discrete rooms or sections. Not all areas of this map are available at the start, often requiring the player to obtain an item (such as a weapon or key) or a new character ability to remove some obstacle blocking the path forward. Often, this item is protected by a boss character, providing story-driven challenges throughout the game. Maps are non-linear, and often require the player to traverse the map multiple times during the course of the game. Weaker monsters will inhabit other parts of the level, re-spawning when the player revisits those rooms, and often can be defeated to gain health, ammunition, or experience points.