The rank of lieutenant has different meanings in different military formations (see comparative military ranks), but the majority of cases it is common for it to be sub-divided into a senior (first lieutenant) and junior (second lieutenant) rank. The NATO equivalent rank for land force officers is OF-1 rank. In navies, while certain rank insignia may carry the name: "lieutenant", the term may also be used to relate to a particular post or duty, rather than a rank.
Before 1871, when the whole British Army switched to using the current rank of "lieutenant", the Royal Artillery, Royal Engineers and fusilier regiments used "first lieutenant" and "second lieutenant".
The first lieutenant (often abbreviated "1st Lt") in a Royal Navy ship 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, unless the ship was complemented with a commander. Although lieutenants are no longer ranked by seniority, the post of "first lieutenant" remains. In minor war vessels, destroyers, frigates, and submarines, the first lieutenant is second in command, executive officer (XO) and head of the executive branch; in larger ships where a commander of the warfare specialization is appointed as the executive officer, a first lieutenant 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. Colloquial terms in the Royal Navy for the first lieutenant include "number one", "the jimmy" (or "jimmy the one") and "James the First" (a back-formation referring to James I of England).
U.S. Army, U.S. Marine Corps and U.S. Air Force
In the U.S. Army, U.S. Marine Corps, and U.S. Air Force, a first lieutenant is a junior commissioned officer. It is just above the rank of second lieutenant and just below the rank of captain. It is equivalent to the rank of lieutenant (junior grade) in the other uniformed services.
Promotion to first lieutenant is governed by Department of Defense policies derived from the Defense Officer Personnel Management Act of 1980. DOPMA guidelines suggest all "fully qualified" officers should be promoted to first lieutenant. A second lieutenant (grade O-1) is usually promoted to first lieutenant (grade O-2) after 18 months in the Army or 24 months in the Marine Corps and Air Force. The difference between the two ranks is slight, primarily being experience and a higher pay grade. It is not uncommon to see officers moved to positions requiring more experience after promotion to first lieutenant. For example, in the Army and Marine Corps these positions can include leading a specialty platoon, or assignment as the executive officer for a company-sized unit (70–250 soldiers or marines). In the Air Force, a first lieutenant may be a flight commander or section's officer in charge with varied supervisory responsibilities, including supervision of as many as 100+ personnel, although in a flying unit, a first lieutenant is a rated officer (pilot, navigator, or air battle manager) who has just finished training for his career field and has few supervisory responsibilities.
Note: U.S. Marine Corps (USMC) first lieutenant insignia bars have squared off edges.
In the U.S. Navy and U.S. Coast Guard, "first lieutenant" is the name of a billet and position title, rather than rank. Officers aboard early sailing ships were the captain and a number of lieutenants. The senior among those lieutenants was known as the first lieutenant, and would have assumed command if the captain were absent or incapacitated. As modern ships have become more complex, requiring specialized knowledge of engineering, communications, and weapons, the "first lieutenant" is the officer in command of the deck department responsible for line handling during mooring and underway replenishment. On smaller ships, the officer of the "first lieutenant" billet holds the rank of lieutenant, junior grade or ensign. On larger vessels, the position of "first lieutenant" is held by a lieutenant or, in the case of extremely large warships such as cruisers or aircraft carriers, the position of "first lieutenant" may be held by a lieutenant commander or even commander. However, on submarines and in aircraft squadrons, where the deck department may only have a few junior sailors, the "first lieutenant" billet may be filled by a first-class petty officer or chief petty officer. What is known in the U.S. Navy as the "first lieutenant division" is usually composed of junior sailors (E-3 and below) who are completing their ninety days of temporary assigned duty, or TAD, that all enlisted personnel are required to perform when initially assigned to a command. The primary mission of the division is servicing, cleaning, organizing and inventorying items within a command.
U.S. Revenue Cutter Service
The term "first lieutenant" had a dual meaning in the U.S. Revenue Cutter Service. The position title of first lieutenant was held by a junior officer who was in charge of deck operations and gunnery. The rank of first lieutenant was the equivalent to lieutenant in the current rank structure of the U.S. Coast Guard and U.S. Navy. The next senior officer ranking above first lieutenant was captain and the next two lower officer ranks were second and third lieutenant, respectively. The rank of first lieutenant carried over to the formation of the U.S. Coast Guard in 1915 and was used until 1918, when the rank structure of the U.S. Navy was adopted.
In Indonesia, "First lieutenant" is known as Letnan Satu (Lettu). The Lieutenant rank has two levels, which are: Second lieutenant (Letda) and First lieutenant (Lettu).
In the Israel Defense Forces, the rank above second lieutenant is simply lieutenant. The rank of (קצין מקצועי אקדמאי (קמ"א (katsín miktsoí akademai or "kama"), a professional academic officer (that is, a medical, dental or veterinary officer, a justice officer or a religious officer), is equivalent to a professional officer of the second class in the reserve and equivalent to first lieutenant.
For other countries, the equivalent rank to a US Army first lieutenant (O-2) is listed below.
- Afghanistan: Lomri baridman
- Albania: Toger
- Angola: Primeiro tenente
- Arabic-speaking countries except former French colonies in North Africa: Mulazim awwal
- Argentina: Teniente primero (army); primer teniente (air force)
- Australia: Army lieutenant (pronounced left-enant); Royal Australian Navy sub-lieutenant (pronounced "loo-tenant")
- Austria: Oberleutnant
- Azerbaijan: Baş leytenant
- Belarus: Старший лейтенант (Russian), старшы лейтэнант (starshy leytenant) (Belarusian)
- Belgium: Lieutenant (French); luitenant (Dutch)
- Bhutan: Deda gom
- Bosnia and Herzegovina: Poručnik
- Bolivia: Subteniente
- Brazil: Primeiro tenente
- Bulgaria: Cтарши лейтенант (starshiy leytenant)
- Cambodia: Ak-no-say-ney-tor
- Canada: Lieutenant
- Cape Verde: Primeiro tenente
- Imperial China (Qing Dynasty): 副軍校 (Fù jūn xiào)
- People's Republic of China: 中尉 (Zhōngwèi)
- Republic of China (Taiwan): 中尉(Chungwei)
- Croatia: Natporučnik
- Cuba: Primer teniente
- Chile: Teniente
- Cyprus: Ypolokhagos (army); yposminagos (air force); anthypoploiarchos (navy)
- Czech Republic (and former Czechoslovakia): Nadporučík
- Denmark: Premierløjtnant
- Dominican Republic: Primer teniente
- Estonia: Leitnant
- Ethiopia: መቶ አለቃ (Meto Aleqa)
- Finland: Yliluutnantti
- France and all other French-speaking countries: Lieutenant (air force/army), enseigne de vaisseau de première classe (navy)
- Georgia: უფროსი ლეიტენანტი (Up’rosi leytenanti)
- Germany: Oberleutnant
- Greece: Ypolokhagos (army); yposminagos (air force); anthypoploiarchos (navy)
- Hungary: Főhadnagy
- Indonesia: Letnan satu
- Iran: ستوان یكم (Setvan yekom)
- Republic of Ireland: Lieutenant (English); lefteanant (Irish)
- Israel: סגן (Segen)
- Italy: Tenente
- Imperial Japan: Rikugun-Chūsa 陸軍中佐
- Japan: Nitō rikui 2等陸尉 (or Nii 2尉) (modern) / Chūi 中尉 (historical)
- Jordan: ملازم أول (Moulazem awal)
- Kazakhstan: Старший лейтенант (Russian), аға лейтенант (Kazakh)
- North Korea and South Korea: 중위 (Jungwi)
- Laos: Roithõäkäd
- Latvia: Virsleitnants
- Lithuania: Vyresnysis leitenantas
- Luxembourg: Premier lieutenant
- Malaysia: Leftenan
- Mexico: Teniente primero
- Nepal: Upa-senani
- Republic of Macedonia: Поручник (poručnik)
- Mongolia: Ахлах дэслэгч (Ahlah deslegch)
- Morocco: "Lkowad"
- Mozambique: Tenente
- Netherlands: Eerste luitenant
- Nicaragua: Teniente primero
- Norway: Løytnant
- Pakistan: Lieutenant (army)
- Paraguay: Teniente primero
- Philippines: First lieutenant (English); pulimagat (Tagalog); primero teniente (Philippine Spanish)
- Poland: Porucznik
- Portugal: Tenente
- Romania: Locotenent (current); locotenent-major (Warsaw Pact)
- Russia: Russian: Старший лейтенант (Starshy leytenant)
- Serbia: Поручник (poručnik)
- Singapore: Lieutenant
- Slovakia: Slovak: Nadporučík
- Slovenia: Nadporočnik
- Somalia: Dagaal
- Spain and all other Spanish-speaking countries except Argentina, Cuba, the Dominican Republic, Nicaragua, Paraguay and Uruguay: Teniente
- Suriname: Luitenant
- Sweden: Löjtnant
- Switzerland: German: Oberleutnant; French: premier-lieutenant; Italian: primotenente
- Thailand: Roi tho
- Tunisia: ملازم أول (moulazem awal)
- Turkey: Üsteğmen
- Ukraine: Ukrainian: Cтарший лейтенант, translit. starshyy leytenant
- Uruguay: Teniente primero
- Uzbekistan: Katta leytenant
- Vietnam: Thượng úy
- Venezuela: Primer teniente
- Yugoslavia: Поручник (poručnik)
- Partridge, p 612, p 621, p 884
- Marine Corps Uniform Regulations, p 4-21
- Hayes, David. "Ranks & Duties". Historic Naval Fiction. Retrieved 22 April 2018.
- Barnebey, Matthew; "1st Lieutenant Division plays significant role in supporting base", Jax Air News
- Cipra, Dave; "A History of Sea Service Ranks & Titles", Commandant's Bulletin, (May, June, July 1985), U.S. Coast Guard Historian's Office.
- References used
- Marine Corps Uniform Regulations, Marine Corps Order P1020.34G with changes 1-5, Chapter 4. Insignia and Regulations for Wear, Sec. 4005. Insignia of Grade, Officers, Para. 2. Description by Grade, h. Captain, i. First Lieutenant, j. Second Lieutenant (p. 4-25) and Figure 4-11. Officers' Grade Insignia (Shoulder/Collar). Washington, DC: United States Marine Corps.
- Barnebey, Matthew (29 June 2011). "1st Lieutenant Division plays significant role in supporting base". Jax Air News. Jacksonville.com website. Retrieved 6 May 2014.
- Cipra, Dave (May 1985). "A History of Sea Service Ranks & Titles" (PDF). Commandant's Bulletin. U.S. Coast Guard Historian's Office. Retrieved 6 May 2014.
- Partridge, Eric (1984). A Dictionary of Slang and Unconventional English (8th ed.). London and New York: Routledge. ISBN 978-0025949805.
|NATO rank code||Student officer||OF-1||OF-2||OF-3||OF-4||OF-5||OF-6
|Royal Navy||O Cdt||Mid||SLt||Lt||Lt Cdr||Cdr||Capt||Cdre||RAdm
|Adm of the Fleet|
|Royal Marines||O Cdt||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen||Lt-Gen||Gen
|Army||O Cdt||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen
|Royal Air Force||Off Cdt / SO||APO / Plt Off||Fg Off||Flt Lt||Sqn Ldr||Wg Cdr||Gp Capt||Air Cdre||AVM||Air Mshl||Air Chf Mshl
|Mshl of the RAF|
|Pay grade / branch of service||Officer
|Army||CDT / OC||2LT||1LT||CPT||MAJ||LTC||COL||BG||MG||LTG||GEN||GA||GAS|
|Marine Corps||Midn / Cand||2ndLt||1stLt||Capt||Maj||LtCol||Col||BGen||MajGen||LtGen||Gen|||||
|Navy||MIDN / OC||ENS||LTJG||LT||LCDR||CDR||CAPT||RDML||RADM||VADM||ADM||FADM||AN|
|Air Force||Cadet / OT / OC||2nd Lt||1st Lt||Capt||Maj||Lt Col||Col||Brig Gen||Maj Gen||Lt Gen||Gen||GAF|||
|Coast Guard||CDT / OC||ENS||LTJG||LT||LCDR||CDR||CAPT||RDML||RADM||VADM||ADM|||||
| No universal insignia for officer candidate rank; Navy candidate insignia shown|
Official 1945 proposal for General of the Armies insignia; John J. Pershing's GAS insignia: ; George Dewey's Admiral of the Navy insignia:
 Rank used for specific officers in wartime only, not permanent addition to rank structure
 Grade is authorized by the U.S. Code for use but has not been created
 Grade has never been created or authorized
 USAF and U.S. Army insignia shown
United States warrant officer ranks
 Grade is authorized for use by U.S. Code but has not been created
 Grade never created or authorized