Aglossia (aglossia congenita) is a congenital defect resulting in a partial development or complete absence of a tongue.

Aglossiais commonly associated with craniofacial and limb defects (Adactylia syndrome) and is thought to belong to a family of oromandibular limb hypogenesis syndrome or OLHS. It is believed to be caused by heat-induced vascular disruption near the fourth week of embryonic development.

The first known case was reported in the early 18th century by a member of the prominent De Jussieu family in France and cases to this day remain rare.

Tongue lesions are very common. For example, in the United States one estimated point prevalence was 15.5% in adults. Tongue lesions are more common in persons who wear dentures and tobacco users. The most common tongue conditions are geographic tongue, followed by fissured tongue and hairy tongue.

Hanhart syndrome (also known as Aglossia adactylia; Hypoglossia-hypodactylia syndrome; Peromelia with micrognathia) is a congenital disorder that causes an undeveloped tongue and malformed extremities and fingers.

Hippocrates, Galen and others considered the tongue to be a "barometer" of health, and emphasized the diagnostic and prognostic importance of the tongue. Assessment of the tongue has historically been an important part of a medical examination. The shape and color of the tongue is examined and observed diagnostically in traditional Chinese medicine. For example, scalloping of the tongue is said to indicate qi vacuity. Some modern medical sources still describe the tongue as "the mirror of physical health". This is related to the high rate of turnover of the oral mucosa compared to the skin, which means that systemic conditions may manifest sooner in the mouth than the skin. Physical appearances such as cyanosis are also often more readily apparent in the mouth.