Spira is the fictional world of the Square role-playing video games Final Fantasy X and X-2. Spira is the first Final Fantasy world to feature consistent, all-encompassing spiritual and mythological influences within the planet's civilizations and their inhabitants' daily lives. The world of Spira itself is different from the mainly European-style worlds found in previous Final Fantasy games, being much more closely modeled on a setting influenced by the South Pacific, Thailand, Bali and Japan, most notably with respect to its vegetation, topography and architecture.

The creation of Spira includes distinct ethnic minorities including a portrayal of the fictional Al Bhed language that is prevalent throughout the game's dialogue. The backstory and concept behind the dark religious themes of Final Fantasy X were a central theme to the story and their ultimate resolution was well received. The popularity of the Eternal Calm video served as the impetus of Square Enix to do Final Fantasy X-2 to make their first direct sequel in video game form and depict the evolution of Spiran society after religious and political upheaval results in new factions and instability in the world. Spira and its inhabiting characters have been featured in several other Square Enix works including Dissidia Final Fantasy and its prequel Dissidia 012, three games within the Kingdom Hearts series and Theatrhythm Final Fantasy.

There have been numerous academic essays on the game's presentation, narrative and localization aspects. Washburn writes that mastering the game comes with the mastering of the cultural knowledge of Spira to unlock skills and abilities. O'Hagan writes on the localization of the games that impact the game experience, detailing alterations to the script and dialogue with modifications, additions and omissions. Another aspect was that the presentation of Spira without an overworld view can be considered a pioneer in 3D role-playing game maps.

In speaking about the inspiration behind Spira, producer Yoshinori Kitase recounted that players had found fault with the science fiction atmosphere of Final Fantasy VII and VIII, instead desiring a "simple fantasy world". To Kitase, the word "fantasy" did not indicate a purely medieval European setting, so he intentionally set out with the objective of redefining the stereotype held in players' minds. Nomura identified the South Pacific, Thailand, and Japan as major influences on the cultural and geographic design of Spira, particularly in regard to the geographic locations of Besaid and Kilika. Yusuke Naora, the art director, noted that during the concept stage many people on the project were interested in Asian themes, including Kitase and writer Kazushige Nojima. The city of Samarkand in Uzbekistan has been cited as an inspiration for Zanarkand.

Nomura said that Spira deviates from the worlds of past Final Fantasy games most notably in the level of detail incorporated, something he has expressed to have made a conscious effort to maintain during the design process. Fumi Nakashima, the sub-character chief designer, concentrated on giving characters from different regions and cultures distinct styles of clothing. Nakashima wanted the machine-oriented society of the Al Bhed to stand out and had them wear masks and goggles to give them a strange and eccentric appearance.

Koji Sugimoto, main programmer for characters, said that the complexities of the PlayStation 2 hardware made mastering it difficult, but more rewarding because the details on Yuna's sleeves to the depiction of shine and shadow could be rendered more realistically. Final Fantasy X was the first game that allowed for 3-D model rendering of backgrounds that increased the presentation, including small details like grass blowing in the wind and cloud movement. Takayoshi Nakazato decided to abandon the typical world map concept for a more realistic depiction. Final Fantasy X's spatial presentation of Spira is tied to progression, with a player's progress being marked through the panoramic introduction and depiction of the area upon first entry. Sound editor Chiharu Minekawa commented that the transition in sound from one environment to the next was done seamlessly to mimic the natural surroundings of these environments as the player moved through them.

The decision to create Final Fantasy X-2 came after fan response to the "Eternal Calm" in the International Edition of Final Fantasy X which depicted events two years following Yuna's final battle. The dark religious theme of the first game was concluded and the cultural changes were explored as the people of Spira focus on fashion that "reflects their state of mind". Toriyama believes the most important element incorporated into X-2 was the "peaceful world of Spira achieved in X and unification of characters' state of mind". Kitase identified Final Fantasy X's theme as "independence from the ties of law and customs" and X-2's theme is about "the changes that occurred from the chaos after gaining that independence".

For Final Fantasy X-2 many pop culture references were used, including Charlie's Angels and with the transformation of the dress spheres being a reference to the magical girl genre of anime.