Lieutenant ( navy ) Lieutenant ( abbreviated Lt , LT , LT ( N ) , Lieut and LEUT ) is a commissioned officer rank in many nations ' navies . It is typically the most senior of junior officer ranks . The rank ' s insignia usually consists of two medium gold braid stripes and often the uppermost stripe features a loop or executive curl . 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 . History . Since at least 1580 the lieutenants in a ship had been the officers 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 introduced the first examination for lieutenant , and it is from the date of this examination that their seniority was set . Lieutenants were numbered by their seniority within the ship , so that a frigate which was entitled to three would have a first lieutenant , a second lieutenant , and a third lieutenant . A first - rate was entitled to six , and they were numbered accordingly . At first a lieutenant ' s commission was given only for the ship in which he served , but after the loss of HMS " Wager " in 1741 and the subsequent mutiny , lieutenants were given full commissions upon passing their examination . During the early days of the naval rank , a lieutenant might be very junior indeed , or might be on the cusp of promotion to captain ; by modern standards he might rank with any army rank between second lieutenant and lieutenant colonel . As the rank structure of navies stabilised , and the ranks of commander , lieutenant commander and sub - lieutenant were introduced , the naval lieutenant came to rank with 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 95 % of lieutenant junior grade should be promoted to lieutenant after serving a minimum of two years at their present rank . Rank insignia . 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 loop is removed . ( see flight lieutenant ) . " First lieutenant " in naval usage . 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 , destroyer s and frigate s 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 the first lieutenant of a capital ship . In the US Navy or US Coast Guard the billet of first lieutenant describes the officer in charge of the deck department or division , depending upon the size of the ship . In smaller ships with 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 .