Background Circular RNAs can serve as regulators influencing the development of pulmonary hypertension (PH). However, their function in pulmonary vascular intimal injury remains undefined. Thus, we aimed to identify specifically expressed circular RNAs in pulmonary microvascular endothelial cells (PMECs) under hypoxia and PH. Methods and Results Deep RNA sequencing and quantitative real‐time polymerase chain reaction revealed that circALMS1 (circular RNA Alstrom syndrome protein 1) was reduced in human PMECs under hypoxia (P