The estrous cycle is a recurring physiological and hormonal process that prepares female domestic animals for ovulation, fertilization and pregnancy. It consists of four major phases—proestrus, estrus, metestrus and diestrus—with each phase characterised by distinct ovarian, reproductive tract and behavioural changes. Based on their cyclic patterns, domestic animals may be classified as polyestrous, seasonally polyestrous or monoestrous. The regulation and expression of the estrous cycle are influenced by several factors, including nutrition and body condition, photoperiod, temperature, age, physical exertion, transportation, systemic diseases, uterine pathology, endocrine disturbances and the presence of males. Understanding these factors is essential for effective reproductive management, early identification of reproductive disorders and improved fertility in farm and companion animals.