Pulmonary hypertension (PH) is a pathophysiological disorder, which may involve multiple clinical conditions and may be associated with a variety of cardiovascular and respiratory diseases. The complexity of managing PH requires a multi-faceted, holistic, and multidisciplinary approach, with active involvement of the patients with PH in partnership with clinicians. In recent years, substantial progress has been made in detecting and managing PH, and new evidence is timely integrated in this fourth edition of the ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. These comprehensive clinical practice guidelines cover the whole spectrum of PH with an emphasis on diagnosing and treating pulmonary arterial hypertension (PAH) and chronic thrombo-embolic pulmonary hypertension (CTEPH).