This paper is an overview of the validation of the total column ozone data products from the Ozone Monitoring Instrument (OMI) onboard the NASA EOS-Aura satellite. OMI is an imaging UV/visible spectrometer that maps global ozone on a daily basis. There are two ozone products from OMI, one derived using the traditional TOMS retrieval algorithm, and another derived using a Differential Optical Absorption Spectroscopy algorithm that is being developed to take advantage of the hyperspectral capabilities of OMI. Validation is primarily performed through comparison with a network of Dobson and Brewer ground stations, and secondarily through campaigns conducted specifically to validate Aura. Comparison with an ensemble of 76 northern hemisphere ground stations shows that OMI-TOMS total column ozone averages 0.4% higher than the station average, with station-to-station standard deviation of ±0.6%. The comparison shows that the OMI-TOMS ozone was stable over the two year period with no evidence of drift relative to the ground network. The OMI-DOAS product is also stable, but with a 1.1% offset and a seasonal variation of ±2%. During four aircraft validation campaigns using the NASA DC-8 and WB-57 aircraft, ozone above the aircraft was measured using an actinic flux instrument and compared with OMI ozone. These comparisons showed agreement within 2% over a broad range of latitude and viewing conditions. Only during the high latitude flights did the OMI-DOAS ozone show the effects of a solar zenith angle dependent error.