Pulmonary hypertension (PH) is highly complex. There are five broad PH clinical categories recognized by the WHO: pulmonary arterial hypertension (PAH, Group 1), PH due to left heart disease (Group 2), PH with lung diseases and/or hypoxia (PH-LD, Group 3), Chronic Thromboembolic Pulmonary Hypertension (CTEPH, Group 4) or other disorders associated with PH (Group 5). This retrospective longitudinal cohort study uses claims data from France (PMSI, SNDS), Germany (SHI Funds), and electronic medical records (EMR) from the UK (CPRD/HES) from Jan-2015 to Dec-2021. The goal is to characterize the epidemiology, the patient profile, the treatment patterns, the resource utilization and the associated costs of PH-LD and the sub-group due to interstitial lung disease (PH-ILD, Group 3.2), and the treatment patterns of PAH patients over the 3-year inclusion period (Jan-2017 and Dec-2019) in the three countries. To identify PH-LD and PAH patients previously published decision trees will be applied to the data sources based on input of clinicians actively treating these patients. In the absence of ICD-10 codes, PH-LD and the sub-group PH-ILD patients will be identified based on the combination of PH-recorded diagnosis with LD/ILD records in the prior 24 months and up to 60 days after the first diagnosis. PAH patients will be identified based on a combination of PH diagnosis, visit to a PH center (if available), Right Heart Catheterization (RHC), and PAH-specific drugs. An estimation of prevalence and incidence will be reported per cohort and country. Patient baseline characteristics and comorbidities will be described, resource use measured, and real-world outcomes, including mortality, presented. Lastly, the treatment patterns will be described for the three cohorts. This pan-European RWE study will provide valuable insights into the epidemiology, management, and real-world outcomes of PAH, PH-LD, and PH-ILD. Limitations associated with claims and EMR data sources apply.