Yellow Diamond

The oldest gem, who mostly does patrol duty. They're partners with Zircon. Yellow Diamond is cheerful yet mature, and feels responsible for all of their siblings.

Throughout their life, Yellow has had several partners—Green Diamond, Ruby, Sapphire, and Pink Topaz—but they were all taken to the moon. Yellow struggles with low self-esteem and possible self-loathing for constantly letting their partners be taken by the Lunarians, and also questions why they bother fighting anymore.

They are one of the gems who accompanies Phos to the moon.

During their time on the moon, Yellow gradually becomes more and more mentally unstable, and eventually even begins to suffer from delusions, thinking of themselves as a Lunarian and becoming distressed whenever they realize they're really a gem.