Species

The world of Steven Universe is filled with many different creatures. This is a catalog of known species.

Gems
Gems are a humanoid species of magical beings. They have many and varied abilities, but all share the trait of having a magic crystal embedded somewhere on their body from which they can summon a special weapon. Gems have the power to shapeshift and are genderless but still use female pronouns. Steven is the first gendered Gem because he is half human. Gems have different special abilities like hydrokinesis or fire resistance. The Crystal Gems are Gems who protect the Earth from Gem based threats.
 * Amethyst
 * Garnet (Fusion Gem)
 * Pearl
 * Rose Quartz
 * Lapis Lazuli
 * Peridot
 * Steven (Half)
 * Opal (Fusion Gem)
 * Sugilite (Fusion Gem)
 * Alexandrite (Fusion Gem)
 * Stevonnie (Fusion Gem, One-Fourth Gem)
 * Jasper
 * Malachite (Fusion Gem)
 * Sapphire
 * Ruby

Humans
Humans are the most populous sentient species on Earth. The humans in Steven Universe seem to be aware of the magical creatures and happenings around them and coexist with them.
 * Steven (Hybrid)
 * Greg Universe
 * Lars
 * Sadie
 * Fryman
 * Peedee Fryman
 * Ronaldo Fryman
 * Jamie
 * Sour Cream
 * Onion
 * Connie Maheswaran
 * Mr. Maheswaran
 * Dr. Maheswaran
 * Kofi
 * Kiki
 * Jenny
 * Nanafua
 * Greg's Uncle (Deceased)
 * Greg's Aunt (Deceased)
 * Yellowtail
 * Mr. Smiley
 * Suitcase Sam
 * Mayor Bill Dewey
 * Buck Dewey
 * Stevonnie (Three-Fourths Human)

Miscellaneous magical creatures

 * Lions:
 * Lion
 * Beetles:
 * Heaven Beetle (corrupted neutral)
 * Earth Beetle (corrupted neutral)
 * Sentient plant life:
 * Watermelon Steven
 * Baby Melon
 * Whales:
 * Tiny Floating Whale (cloud creation)

Miscellaneous non-magical creatures

 * Goats
 * Steven Jr.
 * Steven Jr.'s kids

Corrupted and Broken Gems
Technically not a different species. Corrupted Gems were once normal Gems, but have been corrupted and/or have become broken. Corrupted Gems no longer have the anthropomorphic appearance that normal Gems share, instead they look more feral or monster-like.
 * Giant Pufferfish
 * Worm Monster
 * Centipeetle Mother
 * Gem Cave Creature
 * Ice Monster
 * Invisible Gem Monster
 * Lighthouse Gem Monster
 * Big Bird
 * Tardigrade Gem Monster
 * The Slinker
 * Gem Cave Creature

Corrupted Gem's Minions

 * Drill Parasites
 * Centipeetles

Gem Creatures

 * Crystal Shrimp

Electric Skulls

 * Electric Skulls

Ornithological monsters

 * Unknown Giant Bird (Mentioned in "Cheeseburger Backpack")
 * Giant Bird Egg ("Cheeseburger Backpack")

Spirits

 * Evil Spirit

Robots

 * Robot Shooty Thing
 * Flask Robonoids
 * Plug Robonoids
 * Red Eye

Plants

 * Watermelon Stevens
 * Magic Moss