There are only a handful of potentially life-threatening diagnoses in patients complaining of chest pain and dyspnea. Pneumothorax (PTx) is such a condition. Undiagnosed, pneumothorax can lead to significant morbidity and mortality if not rapidly managed accordingly. Whether caused by a traumatic event or resulting spontaneously, current methods of diagnosis, which include physical exam and chest X-ray, are insensitive in identifying pneumothoraces. Studies on chest radiography for the diagnosis of pneumothorax have routinely revealed sensitivities of approximately 50%. CT, while remaining the gold standard is impractical, expensive, and often not available, while increasing the effects of unnecessary radiation exposure. Lung point-of-care ultrasound (POCUS) has been used for over 15 years, for the accurate and rapid bedside diagnosis of multiple lung pathologies, with sensitivities to diagnose pneumothorax approaching those of CT. In recognizing the presence or absence of lung sliding, B-line artefacts, lung pulse, and lung points, a user of POCUS can detect or rule out pneumothorax with sensitivities well above 95% within a few minutes of the patient encounter. This review will discuss the basic principles of lung ultrasound, the techniques in scanning the supine chest, and review the findings that will help the user rule in and/or rule out pneumothorax rapidly and accurately.