Nemo is the title character, and the tritagonist of the Disney/Pixar movie Finding Nemo. He is the six year old son of Marlin, and the late Coral. He is a clownfish, who has a "lucky fin" (just a birth defect, due to that fin on the right being irregularly smaller than the other). What causes the titular event is that he gets taken by scuba divers, and ends up in a dentist fish tank.
Nemo was voiced by Alexander Gould.