Ovarian tumors, or ovarian neoplasms, are tumors in the ovary. Not all are ovarian cancer. They consist of mainly solid tissue, while ovarian cysts contain fluid.

In 2020, the World Health Organization (WHO) divided ovarian tumours as 90% epithelial, 3% germ cell, and 2% sex cord-stromal types.

Tumor of the ovary vary remarkably as they may arise from any of the 3 cell types of the normal ovary.

Ovarian tumors are classified according to the histology of the tumor, obtained in a pathology report. Histology dictates many aspects of clinical treatment, management, and prognosis.

The most common forms are:

Mixed tumors contain elements of more than one of the above classes of tumor histology.

An 1882 article appearing in Scientific American mentions the case of a patient at University of Pennsylvania Hospital when Dr. William Goodell removed a 112 lbs tumor from a 31 year old patient, who weighted 75 lbs after removal from the tumor.