In the Royal Navy, the rank of midshipman is one of the oldest ranks still in existence, and is the second lowest rank of officer, above that of Officer Cadet. Although not commissioned, midshipmen are officers in the Royal Navy, and rank immediately below Second Lieutenants in the British Army and Pilot Officers in the Royal Air Force and above all enlisted and warrant ranks (since 1956; prior to this a Warrant Officer was considered senior to a Midshipman). A midshipman's rank insignia, which has changed little since Napoleonic times, is a white rhomboid piece of cloth with a gold button and a twist of white cord on each side of the coat collar.

Midshipmen were formerly appointed by warrant or simply entered onto a ship's books, but today, like other subordinate officers, hold their ranks by Admiralty Board orders. In Napoleonic times boys could only be rated midshipmen after two years at sea, after which they were eligible to sit the examination for Lieutenant after a further four years, being at least 19 years of age. Today the rank is only held by officers under the age of 20, at which age they are appointed Sub-Lieutenants (or Acting Sub-Lieutenants where this rank still exists).


In Royal Navy slang, midshipmen are sometimes referred to as "snotties", and a somewhat dubious legend states that the three buttons formerly on the jacket cuffs of the midshipman were placed there to prevent him wiping his nose on his sleeve *.