The asymmetric unit of the title complex, [Mn(C(12)H(6)O(4))(H(2)O)](n), contains one Mn(II) ion, one 1,8-naphthalene-dicarboxyl-ate (1,8-NDC) ligand and one water mol-ecule. The Mn(II) ion is six-coordinated within a distorted octa-hedral coordination geometry, in which the equatorial sites are occupied by four carboxyl-ate O atoms from four different 1,8-NDC ligands, while the axial positions are occupied by two O atoms of two coordinated water mol-ecules. Adjacent Mn(II) centres are bridged by one coordinated water and two carboxyl-ate groups in a syn-syn mode to form infinite chains along the b axis, which are further cross-linked by the naphthalene spacers of the 1,8-NDC ligands to produce a two-dimensional extended network.