Experiments using a diamond-anvil cell show that deuterium sulfide (D2S) dissociates to form sulfur at pressures above 27 GPa and room temperature. Raman-scattering spectroscopy indicates the presence of S-S bonds of a high-pressure phase sulfur, helical sulfur, and eight-membered cyclic sulfur. On the other hand, infrared-absorption spectroscopy indicates the presence of S-D bonds of both polymeric and unreacted D2S. The formation of sulfur from D2S can be interpreted as reconstruction of chemical bonds at high pressures.