The 43rd (6th (City) Battalion, The Royal Northumberland Fusiliers) Royal Tank Regiment (43 RTR) was an armoured regiment of the British Army from 1938 until 1956. It was part of the Royal Tank Regiment, itself part of the Royal Armoured Corps.
It was originally formed by converting the 6th battalion of The Royal Northumberland Fusiliers, a Territorial Army infantry battalion, to a tank unit.