Due to various worldwide energy and environmental issues, such as global warming, energy consumption, and pollution, the sustainable development of human society is facing great challenges. Although tremendous efforts have been made to solve these problems, for example, searching for clean energy resources (solar energy, wind, and nuclear energy, etc.), developing efficient energy storage devices (batteries and supercapacitors), exploring new technologies for air/water purification, and replacing products produced by consuming huge natural resources and causing severe pollutions with environmentally friendly ones, more intensive investigations on developing new highperformance materials are in urgent need in the energy and environment-related fields. [1][2][3] As the most stable crystalline phase of calcium phosphates, hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAP) is the main inorganic component of human bones and teeth. [4] Benefiting from excellent biocompatibility/bioactivity and good biodegradability, HAP biomaterials have been intensively investigated and widely used in the biomedical field, such as drug delivery, protein adsorption, bone regeneration, and bio-imaging. [5][6][7][8][9][10][11][12] There have been some review articles summarizing the biomedical applications of HAP-based biomaterials. [12][13][14][15][16][17][18] However, the studies on energy and environmental applications of HAP nanostructured materials have been seldom reported in the literature. [19][20][21] Recently, one great progress was made by the authors' research group. We developed the calcium oleate precursor solvothermal method for the synthesis of ultralong HAP nanowires (HAP NWs) and invented a new kind of fire-resistant inorganic paper using ultralong HAP nanowires as the building material for the first time. [22][23][24] Different from the traditional cellulose fiber paper which is highly flammable and not resistant to high temperatures, this new kind of fire-resistant inorganic paper exhibits high-biocompatibility, high-flexibility, high-whiteness, excellent resistance to both high temperatures and fire, and can be used for writing and printing. The fire-resistant inorganic paper has various promising applications in a variety of fields such as specialty paper, biomedical, environmental and energy areas. Moreover, the HAP NWs have abundant hydroxyl functional groups on the surface that can be functionalized and modified for different purposes. Owing to these unique properties, HAP NWs have attracted considerable attention for applications in various fields such as biomedical, energy and environment, and many exciting results were reported since then. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Considering the increasing research interest and growing number of publications, it is desirable to provide a timely and systematic overview of recent advances in the studies on HAP NWs and their energy and environmental applications.In this review, we first provide a brief introduction to the synthesis of HAP NWs (Figu...