Diffusion coefficients of hydrogen sulfide in water and brine are critical in geology and chemical indus- tries for hydrogen sulfide geological storage and hydrogen sulfide separation from natural gas. However, previous studies have mostly measured the diffusion coefficient of hydrogen sulfide in water at room temperature and normal pressure and the diffusion coefficient of hydrogen sulfide in brine had not been reported. In this study, ratio of the Raman signal intensity of the H-S bond of hydrogen sulfide to the H –O bond of water, H R H2S / H2O , was used to measure the diffusion coefficients of hydrogen sulfide in water at 0.1–2 MPa and 273.1–373.1 K and in four brine solutions (0.62, 1, 2, and 3 mol • kg −1 NaCl) at 1 MPa and 273.1–373.1 K. Results showed that the diffusion coefficient of hydrogen sulfide in water increased with the increasing temperature and was insignificantly affected by the pressure, which follows the relation- ship derived from the Speedy–Angell power-law: D ( c m 2 /s ) = 13 . 013 ×10 −5 [ T / 216 . 478 −1 ] 1 . 974 , where T is in the temperature (K). In brine, the diffusion coefficient of hydrogen sulfide also increased with the temperature and was clearly inhibited by salinity, which can be described using the Ratcliff–Holdcroft model D ( c m 2 /s ) = 13 . 013 ×10 −5 ( T / 216 . 478 ) 1 . 974 ( 1 −0 . 0755 C s ) , where Cs is concentration of NaCl in brine (mol • kg −1 ).