Steven Quartz Universe is the titular main protagonist of the show Steven Universe. He is the son of Greg Universe and Rose Quartz, and the only member of human descent of the Crystal Gems.
A half-human, half-Gem as a result of his parentage, Steven is an extraordinarily unique being with innate powers beyond that of both normal humans and Gems. While only a child, Steven has steadily grown from an escort of the Crystal Gems into an equal amongst their ranks thanks to his good-hearted nature and resourcefulness. Though he is a part of a monumental legacy, Steven is devoted to fulfilling his destiny as protector of humanity, just like his mother was before him.
Steven is an optimistic, amicable, outgoing, and carefree boy with a happy-go-lucky attitude that is appreciated by many of the citizens of Beach City in one way or another. He is musically inclined, a trait inherited from his father, with a propensity for breaking out into song and (occasionally) playing on his ukulele. Steven is also very kindhearted and compassionate, something which Pearl notes he has inherited from his mother, and he deeply loves his friends and family. He is friendly toward almost everyone he meets, rarely holds grudges, and is very non-discriminatory, never treating anyone with prejudice, even towards his enemies. No matter the situation, Steven will always go out of his way to support his loved ones, even if it means putting his life on the line, and he will avoid resorting to violence. He would much rather choose reasoning than fighting back.
Steven looks up to his caretakers — Garnet, Amethyst, and Pearl — and considers them family. He wants to be a great hero just like them, and he is eager to go on adventures with the trio, both to prove his worth and to have fun exploring strange lands. Despite his under-developed magical power and lack of experience, he has proven himself to have much heroic potential through his resourcefulness, optimism, and confidence.
Steven is rather naïve and socially oblivious, due to his isolated upbringing by the Gems. Steven has never attended a school and, prior to Nightmare Hospital, had never been in a hospital or had his vitals taken. While Steven is often prepared to go on adventures at a moment's notice, he has a habit of biting off more than he can chew, requiring the Gems to intervene. While Steven initially retained his childlike innocence and obliviousness to the dangers he's frequently put in, his encounter with Homeworld Gems gave him a new level of seriousness about being a Crystal Gem. This initially made Steven self-conscious about his immaturity and he resolved to outgrow it, although his misguided attempt would be a source of self-inflicted misery as he tried to break off his friendship with Connie to protect her from harm. It was only Connie's sensible nature that stopped him from going down a bad road.
Like his mother, he appears to be very charismatic; easing a raging crowd, motivating his friends and father in working out, and helping Pearl to find strength to fight Sugilite. His genuine kindness, sincerity and capacity for sympathizing lets him inspire friendship, trust and love from most of the people he meets which enables him to mend others' inner turmoil and reach others who are otherwise closed off, most noticeably in the cases of Peridot and Lapis Lazuli.
Steven is shown to have unique tastes in entertainment. He enjoys the Crying Breakfast Friends! show despite his dad and the Gems' inability to understand its appeal. Steven is bit of a romantic and loved the ending of the The Spirit Morph Saga even when Connie did not agree.
Despite his naivety in some aspects, Steven still has a more grounded and practical outlook than his three caretakers, often correcting them on normal human interactions.
Despite frequently going on many fantastic adventures, Steven has retained a tendency to be easily impressed. He was quickly enamored with Mayor Dewey's play, until Jamie pointed out its flaws. He was also shocked to find that his Watermelon Stevens were alive and admits that it should not have surprised him as much as it did.
While Steven is typically amicable and kindhearted by nature, Steven's enthusiasm and excitability can get out of hand and he ends up doing more harm than good. When this happens, he can be anywhere betwixt obnoxious, overbearing, and simply rude. Steven tends to let his inhibitions go out the window when doing something theatrical. His alter-ego Tiger Millionaire is the best example of Steven letting his passionate side get the better of him.