Charles Fort is a fortification with five bastions intended to mount early artillery. Built between 1677 and 1682 it was also known as New Fort to differentiate it from the nearby James Fort. It contained five bastion with the larger Kinsale and Charles Bastions facing Kinsale Harbour. The concentration of the artillery defences on the sea side contributed to it fall in 1690 after a thirteen day siege by John Churchill. During the Napoleonic War the British decided to move their main operational base from Kinsale to Cork. This was partly due to the silting up of the Kinsale Harbour. Between 1805 and 1812 this transfer to Cork was carried out.
Plans (TNA MFQ 1/520) from 1851 show that at that time it was was called Charlemont, and the Ordnance Department had a store yard just to the South of the Fort itself and also Royal Artillery Barracks to the East of the Fort with a small hospital. Charles Fort itself is shown as Ordnance property with a total area of 29 acres. The buildings in the fort are main shown to be officers quarters with a Governors house and some soldiers barracks.
In 1900 new barracks had been built at Kinsale with a rifle range. The Kinsale Barracks accommodated well over three hundred soldiers. It is assumed that Charles Fort became of limited use after these barracks were built.
With the move of the naval facilities to Cork Harbour by 1812 the defence of Kinsale became of little concern. Fort Charles remained in military hands, armed primarily with smooth bore weapons, but was primarily used as barracks. Fort Charles was never developed and therefore remains a good example of a bastioned fortification.