An embryonal neoplasm arising from the ovary with morphologic features resembling Wilms tumor of the kidney. It occurs during the reproductive age and may present as a rapidly growing adnexal mass. The disease is Monarch Disease Ontology term MONDO_0002230 (ovarian Wilms tumor). Also known as: ovarian Wilms' tumor, ovarian Wilms' tumour, ovary Wilms tumor, ovary Wilms tumour.