The fundamental nature of dark matter remains one of the outstanding mysteries in particle physics more than 90 years after its astrophysical discovery. Cosmic survey experiments can probe the nature of dark matter by measuring the clumping of dark matter on cosmic scales. Spec-S5 will build upon DESI observations and provide a sample of 50 million stellar spectra to explore the particle properties of dark matter as a secondary science goal. Observations from Spec-S5 will be unique and complementary to dark matter studies with other celestial (e.g., Rubin LSST, CMB-S4) and terrestrial (e.g., direct detection, collider, and beam dump) experiments.
