[en] The x-ray-absorption near-edge structure of gas-phase H₂S, hydrogen sulfide, and D₂S, deuterium sulfide, at the sulfur L_2,3 ionization thresholds has been measured using synchrotron radiation with high-energy resolution from the SX700/II soft-x-ray monochromator at the Berliner Elektronenspeicherring-Gessellschaft fuer Synchrotronstrahlung m.b.H. Previously unobserved fine structure is resolved. The spectra of both molecules are characterized by multielectron excitations 8--14 eV above the L₂ threshold energy, broad valence-shell absorption features 5--8 eV below the L₂ edge, and many narrower Rydberg excitations 0--5 eV below the L₂ edge. Comparison of the H₂S and D₂S spectra allows the identification of transitions which include vibrational excitation, due to the isotopic dependence of vibrational energies. For the (2p)^-1 core-excited Rydberg states, a least-squares analysis was employed, which deconvoluted the core-level and excited-orbital splittings. Results show that the twofold degeneracy of the sulfur 2p_3/2 core level is removed by the molecular field, with a resulting splitting of 115 meV for the higher-energy core-excited Rydberg states. The energies of the higher Rydberg states were well described by the Rydberg formula with the quantum defects δ_p=1.63 and δ_d=0.32. Fine structure was resolved in the transitions to the dissociative (2p)^-1 core-excited valence-shell states. The regular spacing and isotopic dependence of this structure clearly identifies it as a vibrational progression