〔Abstract〕 Pulmonary hypertension (PH) is a life-threatening condition characterized by a progressive elevation in pulmonary vascular pressure, ultimately leading to right ventricular dysfunction and failure. The core pathological features of PH include abnormal contraction of small pulmonary arteries and vascular remodeling. In recent years, endoplasmic reticulum stress (ERS), a critical adaptive response of cells to internal and external stressors, has been shown to play a key role in the development and progression of PH. Through the activation of major signaling pathways such as protein kinase R-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6), ERS is directly involved in regulating aberrant cellular behaviors and vascular remodeling in PH. This review systematically discusses the specific role of ERS in the pathogenesis of PH and evaluates its potential as a therapeutic target, aiming to provide a theoretical foundation for novel clinical interventions in PH.