We have used the CFHT 8K x 8K mosaic CCD camera to survey 2.5 square degrees of the Pleiades in R and I to detection limits of about R ~24 and I ~23. This is the deepest, widest area survey for brown dwarfs in the Pleiades conducted to date, covering of order 10% of the effective surface area of the cluster to a sensitivity limit which should allow detection of Pleiades age brown dwarfs to about 0.03 solar mass if the theoretical models are approximately correct. The bright limit for our survey, set by the magnitude where stars saturate in our I band images, corresponds to about 0.12 solar mass at Pleiades age. Of the ~100,000 objects detected in our survey area, we identify sixteen stars as forming a Pleiades brown dwarf sequence in our I vs. R-I color-magnitude diagram. These brown dwarf candidates have I magnitudes ranging from ~17.8 to I ~20, and inferred masses from the hydrogen burning mass limit to about 0.04 or 0.05 Msun. Below I = 20, we no longer see an identifiable locus of Pleiades members in the CM diagram either because few or no objects of this mass formed or because the R-I colors of Pleiades age brown dwarfs change abruptly (grain formation?) at this mass. In any event, by surveying a statistically significant fraction of the Pleiades to very deep limits, we estimate that brown dwarfs are unlikely to compose more than about 2% of the total mass of the Pleiades. If most stars in the galactic disk form in rich clusters, this suggests that brown dwarfs also comprise only a very small fraction of the mass of the disk.