Lieutenant (UK: /lɛfˈtɛnənt/; Lt) is a junior officer rank in the British Army and Royal Marines.

The rank is equivalent to that of a flying officer in the Royal Air Force (RAF).

A typical appointment for a lieutenant might be the command of a platoon or troop of approximately thirty soldiers.

This practice was frowned on outside the trenches but was given official sanction in 1917 as an alternative, being made permanent in 1920 when the cuff badges were abolished.

The cuff badges were: From 1 April 1918 to 31 July 1919, the Royal Air Force maintained the rank of Lieutenant.