The complexity of ovary and fallopian tube pathology is striking, with dozens of tumor types. There is a greater appreciation now of the importance of hereditary cancer syndromes in ovarian and tubal malignancies, as two common autosomal dominant hereditary cancer predisposition syndromes include carcinomas of ovary or fallopian tube. This book is organized following the structure and terminology of the World Health Organization (WHO) classification of Female Genital Tumors, 5th edition. It includes some new entities that have been described since that book's publication in 2020 and provides detailed discussion of differential diagnosis, relevant ancillary tests, and strategies to approach diagnosis. In addition, discussions of the underlying biology of these tumors, as it relates to their diagnosis, are also presented. This fascicle provides an opportunity for deeper reading and quiet reflection about the progress that has been made in our understanding of tumors of the ovary since the previous landmark edition was published in 1998, as well as a respect for the numerous challenges that remain.