Raman spectra of the “molecular” polycrystalline solids HgCl2 (D), HgBr2 (C) and of the yellow form of HgI2 (C) were measured from LN2 up to premelting temperatures. Polarized Raman spectra of molten HgX2 (X = Cl, Br, I) were measured at temperatures up to 950 K. The pure rotational band contour and the vibrational rotational contour of the HgX2 vapors were also measured. Upon melting the vibrational modes of the high temperature solid appear to be preserved. The spectra of the three liquids are similar and are best correlated to the spectra of the D (HgCl2) solid and the vibrational modes of the HgX2 molecules. Reduced Raman spectra of the liquids show splitting of the stretching mode to a doublet, ν1 (A1) and ν1 (B2g), which is attributed to strong intermolecular coupling. The ν2 and ν3 internal modes of the solid are also transferred into the melt. The predominant features of the low frequency reduced spectra is a band, VR, which is assigned to the rotatory modes of the HgX2 molecules and can be correlated to both the rotational band contour of the vapor and the librational modes of the solid. With increasing temperature the spectra of the liquid show softening of the rotatory modes and a blue shift of the ν1 mode, both implying weakening of the intermolecular coupling. An overall decrease in the Raman intensity of the liquid spectra with increasing temperature is attributed to the rapid molar volume increase.