The tokamak is described in its role as a neutron source, with emphasis on experimental results for deuterium-deuterium (D-D) neutron production. Topics covered include tokamak operation, sources of fusion and nonfusion neutrons, principal neutron detection methods and their calibration, neutron energy spectra and fluxes outside the tokamak plasma chamber, history of neutron production in tokamaks, neutron emission and fusion power gain from the Joint European Torus and the Tokamak Fusion Test Reactor (the largest present-day tokamaks), and deuterium-tritium neutron production from burnup of D-D tritons. The prospects for future tokamak neutron production and potential applications of tokamak neutron sources are also discussed.