During an investigation of the SrO-CuO-P2O5-H2O system, single crystals of distrontium hexahydroxidocuprate(II), Sr2[Cu(OH)6], were obtained by the hydrothermal method. The blue prismatic crystals of Sr2[Cu(OH)6] adopt the same structure type as Ba2[Cu(OH)6], Sr2[Zn(OH)6] and Ba2[Zn(OH)6]. The Cu atoms, located at (0, 0, 1/2) (site symmetry 1), form mutually isolated and highly elongated Cu(OH)6 octahedra, which are interconnected to slightly distorted Sr(OH)6 trigonal prisms, forming a layered structure. The location of H atoms from difference Fourier maps and their refinement allowed the precise determination of a three-dimensional hydrogen-bonding network in which all hydroxide O atoms are involved. In addition, the hydrogen-bonding topologies in Sr2[Cu(OH)6] and other similar hexahydroxidometallates with the general formulae M1[M2(OH)6], M1(2)[M2(OH)6] and M1(3)[M2(OH)6] were analysed in detail.