This review provides a broad overview of the structural characteristics, compositional flexibility, and structure-property relationships of hollandite materials. Hollandites have a general formula A x B 8 O 16 , x ≤ 2, with 'A' cations located in one-dimensional tunnels formed by a framework of 'B'-O octahedra. With numerous possibilities for chemical and structural modifications, hollandite family provides many opportunities to manipulate its properties for specific applications. First, we review the chemistry, structure-property relationship, and processing techniques for various applications. The primary focus is on the cumulative effects of Aand B-cation interaction, and the resultant parameters including unit cell symmetry, cation order-disorder, electronic and/or magnetic coupling, that dictate the material's applicability. Then, selected applications, such as crystalline hosts for radioactive caesium disposal, electrode material for Li-ion batteries, and ferromagnetic materials, are outlined from a structure-property relationship perspective. Finally, processing strategies in correlation with structural evolution and applications are briefly addressed.