'Mustang' was an Allied unrealised contingency plan, as an extension of 'Buttress' and in combination with 'Goblet', for a rapid overland advance to Naples in the event of an Italian collapse after the Sicilian campaign (summer 1943).

The plan envisaged the landing of light forces in the 'toe' of Italy for a rapid advance through Calabria for the capture of Naples, through whose port six divisions and 43 squadrons of aircraft could then be landed for a swift progress to Rome.