  We observe the emergence of a disorder-induced insulating state in a strongly
interacting atomic Fermi gas trapped in an optical lattice. This closed quantum
system free of a thermal reservoir realizes the disordered Fermi-Hubbard model,
which is a minimal model for strongly correlated electronic solids. In
measurements of disorder-induced localization obtained via mass transport, we
detect interaction-driven delocalization and localization that persists as the
temperature of the gas is raised. These behaviors are consistent with many-body
localization, which is a novel paradigm for understanding localization in
interacting quantum systems at non-zero temperature.
