Respiratory disease is an umbrella term for diseases of the lung, pleural cavity, bronchial tubes, trachea, upper respiratory tract and of the nerves and muscles of breathing. Respiratory diseases range from mild and self-limiting such as the common cold to life-threatening such as bacterial pneumonia or pulmonary embolism.

Respiratory disease is responsible for over 10% of hospitalizations and over 16% of deaths in Canada. The study of respiratory disease is known as pulmonology. A doctor who specializes in respiratory disease is known as a pulmonologist, a chest medicine specialist, a respiratory medicine specialist, a respirologist or a thoracic medicine specialist.

Respiratory diseases can be classified as either obstructive (i.e. conditions which impede the rate of flow into and out of the lungs, for example asthma) or restrictive (i.e. conditions which cause a reduction in the functional volume of the lungs, for example pulmonary fibrosis).

Respiratory disease can be further classified as either upper or lower respiratory tract (most commonly used in the context of infectious respiratory disease), parenchymal and vascular lung diseases.

In the US, people suffer 1 billion colds per year. One in seven people in the UK is affected by some form of chronic lung disease, most commonly chronic obstructive pulmonary disease and asthma.