Blue Diamond

"How dare you fuse with a member of my court!? You will be broken for this!"

- Blue Diamond angry at Ruby for fusing with Sapphire

Blue Diamond is a major antagonist of the Cartoon Network series Steven Universe. She is one of the Gem Matriarchs on Gem Homeworld and a member of the Great Diamond Authority ruling over Homeworld. She was apparently responsible for overseeing an attempted colonization of Earth, and later, the attempts to quell the rebellion of the Crystal Gems.

She is voiced by the irish singer, Lisa Hannigan.

Appearance
Blue Diamond has a dark navy blue complexion. She has somewhat plump lips and a straight nose. Her gemstone is located on her chest. She wears a long, blue cloak of a slightly lighter shade and more vibrant than her skin, and a dark blue bodysuit with a cutout for her gemstone. She is also noticeably tall in height. This is clearly seen when her Blue Diamond's Pearl is standing next to her. Her mural portrayal from the Moon Base depicts her with either long dark hair or a long cloak.

History
Blue Diamond is one of the members of the Great Diamond Authority alongside Yellow Diamond, Pink Diamond and (presumably) White Diamond. As the matriarchs of Gem Homeworld, she was in charge of colonizing planets for Gem colonizations and expansion.

Season 2
In "The Answer" Blue Diamond appears on-screen for the first time in a Garnet's story narrating how Ruby and Sapphire met each other. It is revealed that she was once the supervisor of the colonization of Earth following the death of Pink Diamond at Rose Quartz's hands. To make sure the progress of colonization was completed, she had a Sapphire predicting the further events to come. However, when Ruby risked her life to save Sapphire's they fused into Garnet and gave enough time for Rose Quartz and Pearl to escape from the battle arena. When this happened, Blue Diamond angrily threatened Ruby that she would be shattered for fusing with one of her court members and for letting the rebels escape. However, Sapphire took Ruby from the hand and left the arena falling to the earth surface in time. Blue Diamond was never seen again through the episode after that.

In "It Could've Been Great", Blue Diamond's mural is seen on the moon base alonside Yellow, White and Pink Diamonds' and is mentioned by Peridot too.

Season 3
In "Back to the Moon", Blue Diamond's mural is once again seen on the moon base when the Crystal Gems and the Ruby Squad went to visit the place.

Season 4
(Coming Soon!)

Season 3
(Coming Soon!)

Trivia

 * Blue Diamond is the first of the Diamonds to be seen on-screen in an episode of Steven Universe.
 * Blue Diamond's appearance and her throne appear to be heavily influenced by Indian Muslim culture. Her clothing resembles that of traditional Arab wedding dress, specifically a Henna dress. The frame of her throne has carved geometrical designs for windows, which are a common design in many Indian temples and houses.
 * She somewhat bears resemblance with Connie's mother.
 * The largest blue diamond, the Hope Diamond, also originates from India.
 * Her appearance in "The Answer" is similar to Emperor Palpatine from Star Wars.