Miss Bitters is a character from the highly popular cartoon series, Invader Zim. She is the teacher of Dib and Zim's class. Devoid of any compassionate emotion, she is a tall, slender aged woman of unknown origin. She displays dark powers, such as the ability to materialize from the shadows. Also seen in Vasquez's earlier Squee! as Tod's teacher. She also seems to transform from a snake-like body, to a normal one, on many occasions. In some early episodes, she has a moustache. As well, she has, on at least one episode, shown a "boot-up" time, taking a few seconds to answer a question as a grinding sound played.

It has been confirmed that Bitters is not human, but not Irken because she did get lice at the end of the episode "Lice!". She was once a fairy princess until she was shocked with a bugzapper in a flashback in "Halloween Spectacular of Spooky Doom". This may have been a lie to horrify the children, as she seems to enjoy lying and evil.

Miss Bitters is voiced by Lucille Bliss .