KOS-MOS (Japanese: コスモス) (recursive acronym for Kosmos Obey Strategical Multiple Operation System) is a fictional character from the Xenosaga role-playing video game series by Monolith Soft and Bandai Namco Entertainment.

According to his wife and Xenosaga writer Soraya Saga, due to how they often depicted human characters in their works as "strong will in a fragile flesh and blood", KOS-MOS was meant to be the opposite, "the delicate pieces of soul in an unbreakable vessel".

In Takahashi's eyes, while normally he would stand by his convictions, he instead felt KOS-MOS "should swing whichever way the wind was blowing" and wanted to aim for an extreme, even providing Mugatani with pictures of one of his favorite pornographic film actresses.

4.0" design of her character is considered the most popular with fans, he himself felt it was the farthest away from the concept he had envisioned, as human influences had started to manifest in her appearance.

One significant change they did from previous versions of KOS-MOS was to have her main laser attack come from her visor instead of her chest at Takahashi's suggestion, and he added temporary "cat ears" to the sides of it to act as heat sinks.

Originally he had considered giving her a "dress" of shorts around her shoulders and hips for a "Gravity Drive" attack, taking inspiration from magical girl anime Pretty Cure, but the development team felt it was excessive and he agreed.

[12][13] That same year, KOS-MOS made a cameo appearance in the role-playing game Tales of Hearts, where she is one of many supporting attack characters for the player.

[16] Numerous figures and figurines of KOS-MOS in various scales have been released in Japan, several of them produced by the company Bandai and cited as being in high demand.

[21] In the 2017 Xeno series entry Xenoblade Chronicles 2, KOS-MOS appears as one of the Rare Blades, an in-game anthropomorphic weapon obtainable via Core Crystals.

Monolith themselves made a self-deprecating reference to the figure in another game, Baten Kaitos Origins, via a boss called "Wicked Gawd".

The staff of UGO.com described her as "widely regarded as one of the most awesome characters to ever come out of Monolith's design department", praising her as single-handedly making the game a pleasure to play due to her "sheer badassitude".

[10] Matt Miller of Game Informer stated that "Amid the strange philosophical and religious overtones" of the series, KOS-MOS stood out as a character that "can't be forgotten", and appreciated the air of mystery around her.

[23] Meanwhile, Stephen Harris of RPGFan praised the symmetry of her appearance and how well she stood out amongst the cast, though did concede that her "scantily clad android" design "will raise more than a few eyebrows the first time she struts her stuff on screen.

Mejia enjoyed how as the series progressed, her dialogue became less robotic and more human, reflecting her own awakening consciousness, and despite being seen as antiquated in the Xenosaga universe due to being an android, she represented the pursuits of attempting to create life strictly from artificial intelligence.

Elliott and Matthew Wilhelm Kapell in the book Playing with the Past saw her relationship with T-elos as an interpretation of Gnosticism, in particular describing the outcome as a "radical reinterpretation of Christian myth", with Mary Magdalene being the one resurrected in the future to protect the universe.

While KOS-MOS throughout the series had gradually developed a more thoughtful and caring personality, T-elos was represented by her passion, pride and anger, due to her biological components.

He additionally pointed out that while she fits the "stoic android learns how to be human" archetype commonly seen in science fiction, her journey through the games helped set her apart, and particularly emphasized how her emotions gave her greater power.