Toothlessness, or edentulism, is the condition of having no teeth. In organisms that naturally have teeth, it is the result of tooth loss.

Organisms that never possessed teeth can also be described as edentulous. Examples are the members of the former zoological classification order of Edentata, which included anteaters and sloths, as they possess no anterior teeth and no or poorly developed posterior teeth.

In naturally dentate species, edentulism is more than just the simple presence or absence of teeth. It is biochemically complex because the teeth, jaws, and oral mucosa are dynamic (changing over time). Processes such as bone remodeling (loss and gain of bone tissue) in the jaws and inflammation of soft tissue in response to the oral microbiota are clinically important for edentulous people. For example, bone resorption in the jaw is frequently how the teeth were able to detach in the first place. The jaw in an edentulous area undergoes further resorption even after the teeth are gone; and the insertion of dental implants can elicit new bone formation, leading to osseointegration. Meanwhile, bacteria and yeasts of the oral cavity and the immune system of their host create an immensely complicated and constantly changing interplay that presents clinically as gingivitis, caries, stomatitis, and other periodontal pathology.