she dismisses Gem fusion as a "cheap tactic to make weak Gems stronger", when she is defeated in battle by fusions she resorts to attempting fusion herself, with disastrous results. Trapped in a fusion by Lapis Lazuli in "Jail Break", the first season finale, she escapes in the third season premiere and becomes a recurring antagonist to the Crystal Gems in the second half of the third season. At the end of the season, she attempts fusion with a corrupted Gem monster, becomes corrupted herself, and is defeated by Steven, Amethyst, and Peridot.

(voiced by Susan Egan)The original leader of the Crystal Gems, Rose Quartz is Steven's mother, who "gave up her physical form" to allow Steven to be born. Her gem is a pink rose quartz that was embedded in her navel. Although she appears only in occasional flashbacks, her legacy and her absence define the lives and relationships of the other main characters. Fascinated by the diversity of life on the planet Earth and the wide range of experiences and growth available to its creatures, she led the ancient rebellion against the Gem Homeworld and its plans to colonize Earth for its resources. The Crystal Gems describe her to Steven as loving and seeing beauty in all forms of life, and flashback episodes show the development of her relationship with Greg from infatuation into love and understanding. Steven feels great pressure to live up to her example as a compassionate leader. His relationship with her memory is complicated at the end of the third season when he learns of morally questionable actions she undertook during the war. "Lion 3: Straight to Video", the first episode in which she appeared (via a videotaped message to Steven), was nominated for an Emmy Award for short-form animation.

(animal noises by Dee Bradley Baker)A mysterious pink lion-like creature who protects Steven and possesses a variety of magical abilities. Lion provides Steven with connections to Rose Quartz's legacy—he brings Steven and Connie to Rose's secret armory, and a number of Rose's keepsakes are stored in a pocket dimension in his mane, including her sword and a videotaped message to Steven—but his origin and the nature of his connection to Rose have not yet been revealed. Steven regards Lion as a pet. Lion is introduced in the early episode "Steven's Lion", in which he appears mysteriously in the desert and follows Steven home.

"Steven Universe" possesses a large cast of occasionally-appearing human characters in Steven's hometown of Beach City, many of whom become the focus of individual episodes that explore their relationships with the main characters and each other. According to critic Sara Goodwin, one of the great strengths of "Steven Universe" as a series is the depth of development it gives to its "normal human being" characters and how the super-powered characters are affected by them.

Recurring human characters include:

(voiced by Uzo Aduba) The Crystal Gems' weaponsmith during the ancient rebellion, Bismuth is passionately devoted to overthrowing the hierarchical structure of Gem society and grateful to Rose Quartz for showing her that an alternative existed. In the show's special hundredth episode, Steven discovers her gem (a bismuth crystal) stored in a bubble in Lion's mane and accidentally frees her. Steven eventually learns that Bismuth was bubbled by Rose as the result of an argument over war tactics: Rose rejected Bismuth's proposed use of a weapon that would permanently destroy enemy Gems, rather than incapacitate them. When the same argument plays out again, Steven is forced to bubble her once more. Aduba's guest performance, and Bismuth's portrayal as a sympathetic character whose complex disagreement with Steven has no easy answers, won praise from critics, although some commentators objected to possible stereotypical implications in the portrayal of a character played by an African-American woman as holding a dangerously militant ideology.

(voiced by Charlyne Yi) – Five Ruby soldiers sent by the Gem Homeworld to locate Jasper during the third season. The five have diverse personalities, but are all played by Charlyne Yi, in a performance that drew praise from critics. They are portrayed as comically gullible, but in the third season finale, when one, a veteran of the war, discovers Steven has the powers of Rose Quartz, she attacks him, vehemently thinking he is Rose Quartz. At the end of the third season, all five Rubies are abandoned to float aimlessly in outer space.

The leaders of the Gem Homeworld and the existing Gem colonies, whom other Gems are created to serve and regard with veneration. Blue Diamond (Lisa Hannigan), who first appears in a flashback in "The Answer", makes her first in-person appearance in the fourth season. Yellow Diamond (Patti LuPone) is shown to be unforgiving and supercilious; at the end of the second season, it is her vindictive disdain towards Earth that led to Peridot's defection to the Crystal Gems. Despite their opposing methods of dealing with various situations, both Blue Diamond and Yellow Diamond are motivated by their mutual grief over Pink Diamond, who is revealed at the end of the third season to have been shattered by Rose Quartz during the rebellion. The existence of a fourth, White Diamond, has been inferred by some viewers, such as The Mary Sue's critic Vrai Kaiser; but if she exists, she has not been mentioned by the characters or writers.

(monster noises by Dee Bradley Baker)An acid-spitting centipede-like corrupted Gem monster that first appeared in the series premiere "Gem Glow", in which the Crystal Gems fought and defeated her and encased her in a bubble. In the mid–first-season episode "Monster Buddies", Steven frees her from her bubble and befriends her; in the third season, he is able to partially and temporarily heal her gem's corruption, and he learns of her history as a member of the Homeworld army who was left behind when the Homeworld Gems fled Earth.

(voiced by Deedee Magno Hall) – A servant Gem caste on Homeworld, belonging to respected Gems. Aside from the principal character Pearl, listed above, pearls belonging to Blue Diamond and Yellow Diamond have appeared in the show to date.

Fusion is a process whereby two or more Gems combine their physical forms and minds to create a larger and more powerful individual, usually for a specific purpose. While the Gem Homeworld allowed Gems of the same caste to fuse, forming a larger version of the components' identical forms, the formation of mixed-Gem fusions is considered offensive. Such a fusion is Garnet, whom Ruby and Sapphire remain fused as most of the time as an expression of their love for each other. Garnet describes the experience of being a fusion in this way: "You are not one person. And you are not two people. You are an experience." The concept of fusion is used by the writers for thematic purposes as a broad metaphor for a range of types of intimacy and relationships.

Mixed-Gem Fusions usually have extra body parts; for example, Garnet has three eyes and Opal has four arms. They are often able to combine the Gem weapons of their component Gems into a more powerful fused weapon.

Garnet is listed above as a main character; below, other fusions are listed in order of appearance.

(voiced by Aimee Mann)The fusion of Amethyst and Pearl. She appears in the early episode "Giant Woman", as Steven's (and the audience's) introduction to the concept of Gem fusion. Amethyst and Pearl rarely fuse, as their conflicting personalities make it difficult for them to achieve the necessary mental and physical harmony. Opal can combine Pearl's spear and Amethyst's whip into a bow.

(voiced by Nicki Minaj)The fusion of Garnet and Amethyst, featured prominently in the first-season episode "Coach Steven". Sugilite's behavior is dangerously violent, as Amethyst and Garnet's personalities when fused together become more unrestrained and aggressive; and she is unwilling to be split back up into Garnet and Amethyst. She can combine Garnet's gauntlets and Amethyst's whip into a giant flail.

(voiced by Rita Rani Ahuja) The combined fusion of Garnet, Amethyst, and Pearl, introduced in the first-season episode "Fusion Cuisine". She is formidable in combat, but confused and unstable when trying to socialize with Connie's parents. She appears in the mobile video game "" as a powerful combined-attack move.

(voiced by AJ Michalka)The fusion of Steven and Connie is the only known instance of a human successfully participating in Gem fusion. Introduced in the first-season episode "Alone Together", Stevonnie has the appearance of a beautiful teenager of indeterminate or nonbinary gender. The character has received critical acclaim both as a rare example of a nonbinary character and as a metaphor by which the writers explore themes of puberty and maturation, consent, and healthy communication.

(Kimberly Brooks ve Jennifer Paz tarafından seslendirilen) Jasper ve Lapis Lazuli'nin bir füzyonu. ilk sezon finalinde, Jasper Crystal Gems'i alt etmek için Lapis'le birleşir, ancak yalnızca Lapis füzyonun kontrolünü alır ve onları okyanusun dibine hapseder. Dengesiz olmasına rağmen, Malachite remains fused until she is defeated in battle by Alexandrite in the third season premiere. In the third-season episode "Alone at Sea", in the aftermath of Malachite's separation, Jasper and Lapis's fusion is used as a metaphor for an abusive relationship.

Rose Quartz ve Pearl'ün füzyonu. Flashback bölümü "We Need to Talk"ta, Greg'in Rose'la samimiyetini kıskançlık seviyesine taşımak için Pearl Rose'la birleşir.

(Alexia Khadime tarafından seslendirilen)Garnet ve Pearl'ün füzyonu, Sardonyx dikkat çeken bir şarkıcıdır ve zarif bir kişiliğe sahiptir. Garnet'in eldivenleri ve Pearl'ün mızrağını birleştirip devasa bir balyoza dönüştürebilir. A major plot arc in the second season, advertised as the "Week of Sardonyx", dealt with Pearl tricking Garnet into fusing for fabricated reasons, and the emotiona