A hydroxyapatite composite is a multiphase biomaterial in which hydroxyapatite, the calcium phosphate mineral Ca10(PO4)6(OH)2 that is chemically and crystallographically analogous to the inorganic phase of natural bone and teeth, is combined with a second constituent to overcome the intrinsic brittleness and low fracture toughness of the monolithic ceramic ^[1]. The reinforcing or second phase may be a bioresorbable polymer such as collagen or polylactide, a second ceramic such as beta-tricalcium phosphate, a bioactive glass, or an inert phase such as zirconia, carbon fibers, or bioglass particles. Because hydroxyapatite itself is osteoconductive and forms a direct bond with living bone while remaining stiff and stable, the composite is designed to retain this bioactive mineral interface while the second phase provides toughness, compliance, or controlled biodegradation. The composite is therefore characterized by a hydroxyapatite matrix or dispersed apatite phase embedded within a continuous secondary phase, with the interface between the two controlling load transfer and dissolution behavior ^[2]. The material is defined structurally as an apatite-containing multiphase solid and functionally as a synthetic analogue of the natural composite architecture in which stiff mineral platelets are bound within a compliant organic matrix ^[3].