Lieutenant[nb 1] (abbreviated Lt, LT, LT(N), Lt(N), Lieut and LEUT, depending on nation) is a commissioned officer rank in many nations' navies. It is typically the most senior of junior officer ranks. In most navies, the rank's insignia may consist of two medium gold braid stripes, the uppermost stripe featuring an executive curl in many Commonwealth of Nations; or three stripes of equal or unequal width.
The now immediately senior rank of lieutenant commander was formerly a senior naval lieutenant rank. Many navies also use a subordinate rank of sub-lieutenant. The appointment of "first lieutenant" in many navies is held by a senior lieutenant.
From at least 1580, the lieutenant on a ship had been the officer immediately subordinate to the captain. Before the English Restoration, lieutenants were appointed by their captains, and this inevitably led to abuses and to the widespread appointment of men of insufficient qualification. In 1677, Samuel Pepys, while he was Chief Secretary to the Admiralty, introduced the first examination for lieutenant, and thereafter their seniority was dated from the passing of this examination.
A lieutenant was numbered by his seniority within the ship on which he served, so that a frigate (which was entitled to three) would have a first, a second, and a third lieutenant. A first-rate ship was entitled to six, and they were numbered accordingly. At first, a lieutenant's commission was given only for the particular ship in which he served, but after the loss of HMS Wager in 1741 and the subsequent mutiny, the Royal Navy changed its policy and lieutenants were given more general commissions upon passing their examination.
During the early days of the naval rank, some lieutenants could be very junior indeed, while others could be on the cusp of promotion to captain; those lieutenants ranged across present-day army ranks from a second lieutenant through to a lieutenant colonel. As the rank structure of navies stabilized, and the ranks of commander, lieutenant commander, and sub-lieutenant were introduced, the rank of naval lieutenant became less wide-ranging and is today the equivalent of an army captain (NATO OF-2 or US O-3).
In the United States Navy, promotion to lieutenant is governed by Department of Defense policies derived from the Defense Officer Personnel Management Act of 1980. DOPMA guidelines suggest that 95% of lieutenants (junior grade) should be promoted to lieutenant after serving a minimum of two years at the lower rank.
The insignia of a lieutenant in many navies, including the Royal Navy, consists of two medium gold braid stripes (top stripe with loop) on a navy blue or black background. This pattern was copied by the United States Navy and various air forces for their equivalent ranks grades, except that the executive curl is removed (see flight lieutenant).
The first lieutenant (1st Lt or 1LT) in the Royal Navy and other Commonwealth navies, is a post or appointment, rather than a rank. Historically, the lieutenants in a ship were ranked in accordance with seniority, with the most senior being termed the first lieutenant and acting as the second-in-command. Although lieutenants are no longer numbered by seniority, the post of "first lieutenant" remains.
In minor war vessels, destroyers and frigates, the first lieutenant (either a lieutenant or lieutenant commander) is second in command, executive officer (XO) and head of the executive branch; in larger ships, where a commander of the warfare specialisation is appointed as the executive officer, a first lieutenant (normally a lieutenant commander) is appointed as his deputy. The post of first lieutenant in a shore establishment carries a similar responsibility to that of the first lieutenant of a capital ship.
In the U.S. Navy or U.S. Coast Guard, the billet of first lieutenant describes the officer in charge of the deck department or division, depending on the size of the ship. In smaller ships that have only a single deck division, the billet is typically filled by an ensign; while in larger ships, with a deck department consisting of multiple subordinate divisions, the billet may be filled by a lieutenant commander. On submarines and smaller Coast Guard cutters, the billet of first lieutenant may be filled by a petty officer.