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Summary Cancer-initiating cells (CICs) have been implicated in tumor development and aggressiveness. In ovarian carcinoma (OC), CICs drive tumor formation, dissemination, and recurrence, as well as drug resistance, thus accounting for the high death-to-incidence ratio of this neoplasm. However, the molecular mechanisms that underlie such a pathogenic role of ovarian CICs (OCICs) remain elusive. Here, we have capitalized on primary cells either from OC or from its tissues of origin to obtain the transcriptomic profile associated with OCICs. Among the genes differentially expressed in OCICs, we focused on CD73, which encodes the membrane-associated 5′-ectonucleotidase. The genetic inactivation of CD73 in OC cells revealed that this molecule is causally involved in sphere formation and tumor initiation, thus emerging as a driver of OCIC function. Furthermore, functional inhibition of CD73 via either a chemical compound or a neutralizing antibody reduced sphere formation and tumorigenesis, highlighting the druggability of CD73 in the context of OCIC-directed therapies. The biological function of CD73 in OCICs required its enzymatic activity and involved adenosine signaling. Mechanistically, CD73 promotes the expression of stemness and epithelial-mesenchymal transition-associated genes, implying a regulation of OCIC function at the transcriptional level. CD73, therefore, is involved in OCIC biology and may represent a therapeutic target for innovative treatments aimed at OC eradication., Graphical Abstract, Highlights • CD73 is enriched in ovarian cancer-initiating cells (OCICs) • CD73 orchestrates OCIC stemness and EMT • OC initiation and growth require CD73 activity • OCIC-associated CD73 is a therapeutic target useful for OC eradication, Cavallaro et al. characterized the transcriptome of OCIC-enriched primary cultures and found CD73 as an upregulated gene. CD73 was then shown to regulate the expression of stemness and EMT-associated genes. The expression and function of CD73 in OCICs is required for tumor initiation, and CD73-targeted drugs decrease the rate of tumor take and inhibit cancer growth.