Fertility preservation (FP) is a rapidly expanding field in reproductive medicine with still limited data on outcomes. FP aims to protect the fertility of children, women, and men who face the potential risk of fertility loss for various medical conditions, including but not limited to cancer and its gonadotoxic treatment forms. Therefore, it is crucial to provide evidence-based recommendations to assist health professionals in discussing FP options. Our aim was to provide a guideline for multidisciplinary medical staff in considering the availability of FP options and to help them decide whether to provide FP. The objective of any FP intervention is to minimize or eliminate primary disease burden and to ensure the maintenance or preserving reproductive health. Therefore, people who are at risk of losing fertility should be evaluated for and counseled about future reproductive risks. Embryo, oocyte, and ovarian tissue cryopreservation are the established FP options in adult females, with ovarian tissue cryopreservation the only option for prepubertal girls. A wide range of variables affect the choice of the FP strategy. These include age and ovarian reserve of women, the time available before the initiation of cancer treatment, pubertal status, and cancer type and stage. In males, sperm cryopreservation is a highly effective method in adolescent and adult males, while testicular tissue cryopreservation, which is experimental, is the only available option for prepubertal males. This review addressed the important clinical questions and provided answers for FP in females, males, and children according to the indications and availability of FP. © 2026 Japan Society of Obstetrics and Gynecology.