The great majority of uterine mesenchymal neoplasms are leiomyomas. Leiomyomas are the most common benign pelvic tumors in women, and they represent the most common indication for hysterectomies in the United States. Leiomyomas may display a variety of growth patterns and macroscopic or microscopic features that may cause them to be mistaken for a malignancy by the pathologist. Others, such as fumaratase hydratase-associated leiomyomas, may have implications to the patient for genetic counseling and should accordingly be recognized. Mesenchymal malignancies of the uterine corpus are rare, and most are leiomyosarcomas and endometrial stromal sarcomas. There have been significant recent advances in identifying subsets of endometrial stromal sarcomas with a molecular basis, which increasingly allows for the correct classification of cases that have previously been erroneously classified as undifferentiated uterine sarcoma or leiomyosarcoma. This chapter also illustrates and discusses various other rare mesenchymal tumors, as well as adenomatoid tumor.