The total neutron cross section of Pu239 has been measured at seventeen neutron energies between 0.00291 ev and 0.10 ev with a crystal spectrometer. The absorption cross section was obtained by subtracting the relatively small scattering cross section from the measured total cross section. The sample used was a plutonium-aluminum metallic foil containing 1% aluminum. The isotopic content of the plutonium was 99.82% Pu239, 0.15% Pu240, and 0.03% Pu241. The value obtained for the absorption cross section of Pu239 at 2200 meters/sec was σa = 1007 ± 8 barns.