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Bulk samples of MgB2 doped with 0, 1, 3, and 5 wt% Pr6O11 nanopowder were prepared using a solid-state reaction route. The lattice constants of Pr6O11-doped MgB2 systematically increase with increasing doping level, indicating a partial substitution of Pr for Mg in the crystal structure, and consequently, the superconducting transition temperature, Tc, of MgB2 is slightly suppressed. At a low doping level of 1 wt% Pr6O11, the critical current density, Jc, and the irreversibility field, Hirr are improved. However, at higher doping levels, Pr6O11 doping seems harmful for the performance of MgB2 in high magnetic fields. It is argued that the effect of the doping mechanism of Pr6O11 on Tc and Jc is quite different from those of other rare-earth elements, such as Y or Dy.