4-Hy­droxy-3-meth­oxy­benzaldehyde thio­semicarbazone

In the title compound, C₉H₁₁N₃S, there is an intra­molecular O—H...O hydrogen bond involving the OH group and the adjacent methoxy O atom. The mol­ecule is essentially planar, with the maximum deviation from the mean plane of the non-H atoms being 0.1127 (14) Å for the methyl C atom. In the crystal, mol­ecules are connected via centrosymmetric pairs of N—H...S and O—H...O hydrogen bonds into a two-dimensional network parallel to (10-3).