Mucinous tumors of the ovary represent a spectrum of neoplastic disorders, including benign mucinous cystadenoma, pseudomyxoma peritonei, mucinous tumors of low malignant potential (borderline), and invasive mucinous ovarian carcinoma. These tumors are related closely to each other and are distinct from other histologic subtypes of epithelial ovarian neoplasms from a clinical, histologic, and molecular standpoint. A continuum appears to be present from benign to borderline to malignant, which is different from other types of epithelial ovarian cancer. Mutational profiles are also distinct, as KRAS mutations are common, but p53 and BRCA mutations are infrequent. These characteristics lead to specific biologic behavior and guide both clinical management and research efforts in patients with mucinous ovarian tumors.