Kussmaul breathing is the rapid, deep, and labored breathing of people who have acidosis. Kussmaul breathing is named for Adolph Kussmaul, the 19th century German doctor who first noted it. It is also called "air hunger".

The cause of Kussmaul breathing is respiratory compensation for a metabolic acidosis, most commonly occurring in diabetics in diabetic ketoacidosis. Blood gases on a patient with Kussmaul breathing will show a low p_CO2 because of a forced increased respiratory rate (blowing off the carbon dioxide). The patient feels an urge to breathe deeply, and it appears almost involuntary.

The effect can be reproduced, to a degree, by rapidly breathing in the air from a recently finished plastic soft-drink bottle (which is rich in carbon dioxide).