We report the detection of CO (3 r 2) emission from the submillimeter-selected luminous galaxy SMM J1401110252. The optical counterpart of the submillimeter source has been identified as a merger system with spectral characteristics consistent with a starburst at z 5 2.565. The CO emission confirms the optical identification of the submillimeter source and implies a molecular gas mass of M,5#1010 h22 , after correcting 75 for a lensing amplification factor of 2.75. The large molecular gas mass and the radio emission are consistent with the starburst interpretation of the source. These results are similar to those found for SMM J0239920136, which was the first submillimeter-selected CO source found at high redshift. The CO detections of these two high-redshift submillimeter galaxies suggest the presence of massive reservoirs of molecular gas, which is consistent with the inferred high rates of star formation (103 M, yr21). These two systems appear to be associated with merger events which may evolve into present-day luminous elliptical galaxies.