"Neptune" was the first British ship to spot the Italian Fleet in the battle of Calabria, on 9 July 1940, marking also the first time since the Napoleonic Wars that the Mediterranean Fleet received the signal "enemy battle fleet in sight". During the subsequent engagement, she was hit by the Italian light cruiser . The 6-inch shell splinters damaged her floatplane beyond repair, its wreckage being thrown into the sea. Minutes later her main guns struck the heavy cruiser "Bolzano" three times, inflicting some damage on her torpedo room, below the waterline and the "B" turret.