  Relativistic and resonance effects in the photoionization of Mg-like Fe~XV
are investigated using the Breit-Pauli R-matrix Method (BPRM) at near-threshold
and intermediate energies, complemented by the Relativistic Random Phase
Approximation (RRPA) and multi-channel quantum defect theory in the energy
region up to the L-shell ionization thresholds. The cross sections exhibit
extensive resonance structures that considerably enhance the effective
photoionization of Fe~XV. These results should be of general interest in
photoionization modeling of X-ray sources observed by space observatories.
