A wheeze is a clinical symptom of a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed (for example narrowing of the lower respiratory tract in an asthmatic attack), or airflow velocity within the respiratory tree must be heightened. Wheezing is commonly experienced by persons with a lung disease; the most common cause of recurrent wheezing is asthma, though it can also be a symptom of lung cancer, congestive heart failure, and certain types of heart diseases.

The differential diagnosis of wheezing is wide, and the reason for wheezing in a given patient is determined by considering the characteristics of the wheezes and the historical and clinical findings made by the examining physician.

The term "wheeze" is also used as a clinical condition describing wheezing in preschool children, termed as "preschool wheeze".