A non-rebreather mask (NRB, non-rebreather, non-rebreather facemask, etc.) is a device used in medicine to assist in the delivery of oxygen therapy. A NRB requires that the patient can breathe unassisted, but unlike a low-flow nasal cannula, the NRB allows for the delivery of higher concentrations of oxygen. An ideal non-rebreather mask does not permit air from the surrounding environment to be inhaled, hence an event of a source gas failure (e.g., the oxygen tank being drained completely) is life-threatening.

The non-rebreather mask is utilized for patients with physical trauma, chronic airway limitation, cluster headache, smoke inhalation, and carbon monoxide poisoning, or any other patients who require high-concentration oxygen, but do not require breathing assistance. Patients uncomfortable with having a mask on their face, such as those with claustrophobia, or patients with injuries to the mouth are more likely to benefit from a nasal cannula, or passive (“blow-by”) oxygen. Patients who are unable to breathe on their own would require invasive or noninvasive mechanical ventilation.