Abstract: SLC7A11, a member of the solute carrier family (Solute Carrier Family 7 Member 11), encodes the light chain subunit SLC7A11 (also known as xCT) of the cystine/glutamate antiporter system x_c^-. SLC7A11 promotes glutathione synthesis through the uptake of cystine and the concomitant release of glutamate. This, in turn, protects cells from oxidative stress, maintains cellular redox balance, and prevents cell death induced by lipid peroxidation. SLC7A11, recently identified as a potential target for cancer therapeutics, is overexpressed in multiple malignant tumors. In addition, it is closely associated with the growth, prognosis, metastasis, and treatment response of multiple types of cancer, including glioblastoma, breast cancer, ovarian cancer, liver cancer, and lung cancer. Emerging insights into the role of SLC7A11 in malignant tumors are summarized in this review.