Osteoporosis poses a significant global health concern, affecting both the elderly and young individuals, including athletes. Despite the development of numerous antiosteoporotic drugs, addressing the unique needs of young osteoporosis patients remains challenging. This study focuses on young rats subjected to ovariectomy (OVX) to explore the impact of high-molecular-weight hyaluronan (HA) on preventing OVX-induced osteoporosis. Twenty-four rats underwent OVX, while 12 underwent sham procedures (sham control group). Among the OVX rats, half received subcutaneous injections of HA (MW: 2700 kDa) at 10 mg/kg/week into their backs (OVX-HA group), whereas the other half received saline injections (0.5 ml/week) at the same site (OVX-saline group). OVX-HA group exhibited significantly higher percentages of osteoclast surface (Oc. S/BS), osteoblast surface per bone surface (Ob. S/BS), and bone volume/tissue volume (BV/TV) compared with OVX-saline group at the same age. The proportions of Ob. S/BS and BV/TV in the OVX-HA group closely resembled those of the sham control group, whereas the proportion of Oc. S/BS in the OVX-HA group was notably higher than that in the sham control group. In summary, the administration of HA significantly mitigated bone resorption and enhanced bone formation, suggesting a crucial role for HA in the treatment of young adult osteoporosis.