The underlying mechanisms by which cellular metabolism affects cervical cancer cell radiosensitivity remain poorly understood. Here, we found that loss of 3-hydroxy-3-methylglutaryl coenzyme A synthase 1 (HMGCS1), a key enzyme catalyzing the conversion of acetoacetyl-CoA to HMG-CoA in the cholesterol biosynthesis pathway, sensitizes the cervical cancer cells to radiation. We observed a compartmentalized cellular distribution of HMGCS1 in nuclei, cytosol, and mitochondria of cervical cancer cells and found that cytosolic HMGCS1 and mitochondrial HMGCS1 contribute together to the regulation of radiosensitivity. Mechanistically, we show that cytosolic HMGCS1 regulates radiosensitivity via manipulating the cholesterol metabolism, while mitochondrial HMGCS1 controls mitochondrial gene expression, thereby sustaining the mitochondrial function of cervical cancer cells. Together, our study identifies HMGCS1 as a novel regulator of radiosensitivty in cervical cancer cells, providing a molecular link between altered cholesterol metabolism, mitochondrial respiration, and radiosensitivity. Thus, targeting HMGCS1 may improve the therapeutic outcome of cervical cancer radiotherapy.Copyright © 2022 Elsevier Inc. All rights reserved.