A flea is a type of insect commonly found on Earth.

Leonard McCoy described the HMS Bounty as a "Klingon flea trap." James T. Kirk, however, reminded him that they "could learn a thing or two from this flea trap," because it possessed a cloaking device. (Star Trek IV: The Voyage Home)

Other types of fleas not commonly found on Earth include:

• Blood flea
• Belzoidian flea
• Melvaran mud flea
• Photonic flea