Absolute photodetachment cross sections for ${\mathrm{He}}^{\ensuremath{-}}^{4}P^{o}$ have been obtained at discrete photon energies between 0.12 and 4.0 eV by normalizing the He photodetachment products from a 1.3-keV ${\mathrm{He}}^{\ensuremath{-}}$ beam to those from autodetachment over a known path length, and making use of the known metastable lifetimes. The cross section reaches 1.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ at 0.12 eV (40 meV above threshold), falls to 1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}17}$ ${\mathrm{cm}}^{2}$ at 4.0 eV, and exhibits several distinct features associated with excited He product states.