We show that proton storage ring experiments designed to search for proton electric dipole moments can also be used to look for the nearly dc spin precession induced by dark energy and ultralight dark matter. These experiments are sensitive to both axion-like and vector fields. Current technology permits probes of these phenomena up to 3 orders of magnitude beyond astrophysical limits. The relativistic boost of the protons in these rings allows this scheme to have sensitivities comparable to atomic comagnetometer experiments that can also probe similar phenomena. These complementary approaches can be used to extract the microphysics of a signal, allowing us to distinguish between pseudoscalar, magnetic and electric dipole moment interactions.