Background/Objectives: Fertility preservation (FP) spans oncological and non‑oncological indications, including gonadotoxic therapies, benign haematological/metabolic disorders, conditions at risk of premature ovarian insufficiency, severe andrological disease, and elective plans to defer childbearing. We provide a sex‑integrated overview of established and emerging FP strategies and their real‑world effectiveness [1–10]. Methods: Narrative synthesis of guidelines and high‑quality studies (to 2025), prioritising ASCO/ESHRE guidance, systematic reviews, and multicentre/registry data covering oocyte/embryo cryopreservation, ovarian tissue cryopreservation (OTC), GnRH agonists, ovarian transposition, in vitro maturation (IVM), sperm banking, surgical sperm retrieval (SSR), testicular tissue cryopreservation (TTC), and spermatogonial stem‑cell (SSC) approaches [1–10]. Results: For women, oocyte vitrification is the first‑line option when time allows; OTC is established when stimulation is infeasible or in prepubertal girls, with endocrine recovery common and increasing pregnancy/live‑birth reports. For men, sperm cryopreservation before therapy is standard; SSR supports selected cases. Paediatric TTC is feasible but remains experimental, whereas paediatric OTC is clinically implemented. Random‑start COS and letrozole/tamoxifen protocols minimise treatment delay and hormonal exposure; GnRHa co‑treatment preserves ovarian function as an adjunct. Utilisation of banked gametes/tissue remains modest, underscoring the need for pathway optimisation [1–10]. Conclusions: FP should be embedded across oncology and non‑oncology pathways with timely referral, clear counselling on probabilities of live birth, and robust follow‑up. Standardisation, registry‑based evidence and long‑term offspring safety data are priorities to bridge the gap between laboratory potential and clinical effectiveness [1–10].