An integrated process for co-producing phosphorus pentafluoride (PF.sub.5) and fluorosulfonic acid (HSO.sub.3F) in high yield and purity via a single reaction step is provided. The method includes reacting a first reagent comprising an aqueous solution of hexafluorophosphoric acid (HPF.sub.6) and hydrofluoric acid (HF) with a second reagent comprising fuming sulfuric acid (H.sub.2SO.sub.4.Math.SO.sub.3) and recovering a product mixture comprising phosphorus pentafluoride (PF.sub.5) and fluorosulfonic acid (HSO.sub.3F).