We report Stimulated Brillouin gain spectra of bulk superfluid helium-4. Stimulated Brillouin gain spectroscopy is a powerful optical method to probe the acoustic properties of liquid helium in a narrow spatio-temporal domain with moderate optical power and fast acquisition rates. We determine the velocity of first sound of superfluid helium-4 from the Stimulated Brillouin gain spectra between 0.90 K and 2.17 K and compare it to well known available data, which validate our experimental method.