Laboratory measurements of the cross sections for double ionization of atomic oxygen by electrons are presented for collision energies from threshold to 4eV. This process displays a maximum cross section of about .5 A^2 at a collision energy of approximately 2eV. These absolute cross sections were obtained from measurements of the ratio of the cross sections for double and single ionization, coupled with absolute cross sections for single ionization previously measured by other investigators. The configuration and operation of the apparatus for these measurements are described. Procedures used to assess the effects of oxygen excited states on the measurements are reported.