Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope O-23. The O-22 fragments produced in one-nucleon removal from O-23 at 938 MeV/nucleon in a carbon target were detected in coincidence with deexciting gamma rays. The widths of the longitudinal momentum distributions of the O-22 fragments and the one-neutron removal cross sections were interpreted in the framework of a simple theoretical model which favors the assignment of I-pi=1/2(+) to the O-23 ground state.