Ovarian reserve is a complex clinical phenomenon influenced by age, genetics, and environmental variables. Although it is challenging to predict the rate of an individual’s ovarian reserve decline, clinicians are often asked for advice about fertility potential and/or recommendations regarding the pursuit of fertility treatment options. The purpose of this review is to summarize the state-of-the-art of ovarian reserve testing, providing a guide for the obstetrician/gynecologist generalist and reproductive endocrinologist. The ideal ovarian reserve test should be convenient, be reproducible, display little if any intracycle and intercycle variability, and demonstrate high specificity to minimize the risk of wrongly diagnosing women as having diminished ovarian reserve and accurately identify those at greatest risk of developing ovarian hyperstimulation prior to fertility treatment. Evaluation of ovarian reserve can help to identify patients who will have poor response or hyperresponse to ovarian stimulation for assisted reproductive technology. Ovarian reserve testing should allow individualization of treatment protocols to achieve optimal response while minimizing safety risks. Ovarian reserve testing may inform patients regarding their reproductive lifespan and menopausal timing as well as aid in the counselling and selection of treatment for female cancer patients of reproductive age who receive gonadotoxic therapy. In addition, it may aid in establishing the diagnosis of polycystic ovary syndrome and provide insight into its severity. While there is currently no perfect ovarian reserve test, both antral follicular count and antimüllerian hormone have good predictive value and are superior to day-3 follicle-stimulating hormone. The convenience of untimed sampling, age-specific values, availability of an automated platform, and potential standardization of antimüllerian hormone assay make this test the preferred biomarker for the evaluation of ovarian reserve in women.