Folate receptor 1 (Folate receptor alpha, FOLR1) is a protein that in humans is encoded by the FOLR1 gene. The protein encoded by this gene is a member of the folate receptor (FOLR) family. Members of this family have a high affinity for folic acid and for several reduced folic acid derivatives, and mediate delivery of 5-methyltetrahydrofolate to the interior of cells. FRα, due to its high expression in some tumors, is an attractive therapeutic target for the development of novel anti-cancer agents in order to limit toxic side-effects on off-target tissues. FRa can be overexpressed by a number of epithelial-derived tumors including ovarian, breast, renal, lung, colorectal, and brain. Therefore, antibodies to FRa are being developed for use in targeted therapies, with one example being farletuzumab, in a phase III trial for ovarian cancer.