Fertility preservation (FP) comprises a growing array of medical, surgical, and biotechnological strategies that safeguard reproductive potential in individuals facing gonadotoxic treatments, systemic diseases, or age-related fertility decline. With advances in cryobiology, assisted reproductive technologies, and a deeper understanding of gonadal physiology, FP has transitioned from an experimental practice primarily targeting oncology patients to a mainstream component of reproductive medicine. Current FP methods including oocyte and embryo cryopreservation, ovarian tissue cryopreservation, sperm banking, and in selected cases pharmacological ovarian suppression are implemented according to age, diagnosis, treatment urgency, and available reproductive material. For males, sperm cryopreservation remains the most reliable and effective technique, while testicular tissue storage is reserved for research protocols in prepubertal boys. For females, vitrification has markedly improved survival and pregnancy rates, positioning oocyte cryopreservation as an established option equivalent to embryo freezing. Ovarian tissue cryopreservation represents the only feasible approach for prepubertal girls and for patients requiring urgent therapy without stimulation. Emerging technologies such as in vitro gametogenesis, artificial ovary systems, and stem cell–derived gametes hold promise for expanding future reproductive options, particularly for patients for whom current methods are inadequate. Ethical considerations including informed consent in minors, risk of malignant cell reintroduction, and equitable access remain central to FP practice. From a sustainability perspective, FP supports long-term reproductive autonomy, psychological well-being, and social continuity by enabling individuals to maintain fertility despite medical or environmental challenges. Integrating FP into sustainable health frameworks underscores its role not only as a medical intervention but also as a contributor to broader public health, ethical governance, and human development.