In this chapter, the anatomy, histology and salient non neoplastic lesions of ovary have been discussed. It is necessary to have detailed knowledge of ovarian histology to provide report on non-neoplastic ovarian lesions. Ovary is located outside the pelvic cavity in new born. It descends progressively and lies on each side of the uterus in prepubertal period. Cortex and medulla are two parts of ovary. The ovarian cortex is composed mainly of specialized stromal cells arranged in small bundles in whorls and storiform pattern. Medulla of the ovary is highly vascular area and is composed of loose fibroblasts, large blood vessels, lymphatics and nerves. This chapter also discusses the follicle and derivatives, infections of ovary, non-neoplastic lesions of the follicular and stromal elements, and polycystic ovarian syndrome. This chapter also explains about the stromal hyperplasia and stromal hyperthecosis, hilus cell hyperplasia, massive stromal edema and fibromatosis, ovarian decidua (ectopic decidua) and pregnancy luteoma. Ovarian torsion and infarction, ovarian failure and congenital lesions of ovary are also discussed in this chapter.