Physiognomy (from the Greek φύσις, 'physis', meaning "nature", and 'gnomon', meaning "judge" or "interpreter") is the practice of assessing a person's character or personality from their outer appearance—especially the face. The term can also refer to the general appearance of a person, object, or terrain without reference to its implied characteristics—as in the physiognomy of an individual plant (see plant life-form) or of a plant community (see vegetation).

Physiognomy as a practice meets the contemporary definition of pseudoscience and it is so regarded among academic circles because of its unsupported claims; popular belief in the practice of physiognomy is nonetheless still widespread and modern advances in artificial intelligence have sparked renewed interest in the field of study. The practice was well-accepted by ancient Greek philosophers, but fell into disrepute in the Middle Ages while practised by vagabonds and mountebanks. It revived and was popularised by Johann Kaspar Lavater, before falling from favor in the late 19th century. Physiognomy in the 19th century is particularly noted as a basis for scientific racism. Physiognomy as it is understood today is a subject of renewed scientific interest, especially as it relates to machine learning and facial recognition technologyThe main interest for scientists today are the risks, including privacy concerns, of physiognomy in the context of facial recognition algorithms.

Physiognomy is sometimes referred to as 'anthroposcopy', a term originating in the 19th century.