Quantum Molecular Dynamics simulations of protactinium (V) fluoro and oxofluoro complexes in solution were undertaken using density functional theory with generalised gradient approximation (and the ABINIT software package). The complexes were studied in the gas phase (at 0 K) and in solution (at 298 K) with water molecules as the solvent. We characterised all of the systems, taking into account their structures, dissociation energies, bond lengths and formation enthalpies in solution, and explained their relative stabilities. At ambient temperature, the hydrated species PaF 5 , P a F 4 + $Pa{F}_{4}^{+}$ , P a O F 5 2 − $PaO{F}_{5}^{2-}$ , P a O F 4 − $PaO{F}_{4}^{-}$ and PaOF 3 were found to be the most stable (and to exhibit similar stabilities). The calculated formation enthalpies of the complexes are in close agreement with measurements made elsewhere.