The title 1,3,4-oxadiazole derivative crystallizes as a hemihydrate, C8H6N2O2S·0.5H2O, with the water molecule located on a twofold rotation axis. The 1,3,4-oxadiazole molecule is essentially planar, the r.m.s. deviation of the non-H atoms being 0.0443 Å. The dihedral angle between the mean planes of the phenyl and oxadiazole rings is 6.101 (17)°. In the crystal, molecules are linked via O—H...S and N—H...O hydrogen bonds involving the water molecule, the N—H group and the thione S atom into undulating ribbons. Additional π–π interactions generate a two-dimensional supramolecular framework extending parallel to (001).