Flatworms are classified as Platyhelminthes. Platyhelminthes is a phylum of soft-bodied, flattened worms that includes flatworms. They are characterized by their flattened body shape and lack of a true coelom (body cavity). Flatworms can be found in a variety of environments, including freshwater, marine, and terrestrial habitats. They are also known for their ability to regenerate lost body parts, which is a unique characteristic among animals.