For the moth genus, see Mormo (moth).

In Greek mythology, Mormo (Greek:Μορμώ, Μορμών, Mormō) was a spirit who bit bad children, and was said to have been a companion of the goddess Hecate. The name was also used to signify a female vampire-like creature in stories told to Greek children by their nurses to keep them from misbehaving. This reference is primarily found in some of the plays of Aristophanes. Mormo is also referenced in The Alexiad, which goes to show that Mormo was still taught to children during Byzantine times. The Mormo would steal children in revenge of Queen Laestrygonian who was deprived by her children.