Lieutenant (junior grade), commonly abbreviated as LTJG or, historically, Lt. (j.g.) (as well as variants of both abbreviations), is a junior commissioned officer rank of the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, and the National Oceanic and Atmospheric Administration Commissioned Officer Corps (NOAA Corps). LTJG has a US military pay grade of O-2, and a NATO rank code of OF-1a. The rank is also used in the United States Maritime Service. The NOAA Corps's predecessors, the United States Coast and Geodetic Survey Corps (1917–1965) and the Environmental Science Services Administration Corps or ESSA Corps (1965–1970), also used the rank.
Lieutenant, junior grade, ranks above ensign and below lieutenant and is equivalent to a first lieutenant in the other uniformed services (the Army, Marine Corps and Air Force) and sub-lieutenant in the Royal Navy and the navies of many Commonwealth countries.
Promotion to LTJG is governed by Department of Defense policies derived from the Defense Officer Personnel Management Act of 1980. DOPMA guidelines suggest all "fully qualified" ensigns should be promoted to LTJG. The time for promotion to LTJG is a minimum of two years after commissioning in the Navy or 18 months in the Coast Guard. Lieutenants, junior grade typically lead petty officers and non-rated personnel, unless assigned to small aircraft or on staff duty. A LTJG's usual shipboard billet is as a division officer.
- Neil Armstrong, Korean War Naval Aviator and as an astronaut, Commander of Apollo 11
- Paul Brown, exceptional High School, College and Pro level American Football Coach
- George H. W. Bush, World War II Naval Aviator and 41st President of the United States
- Albert David, only Atlantic Fleet sailor awarded the Medal of Honor in World War II
- Kirk Douglas, American actor
- Henry Fonda, American film and stage actor
- L. Ron Hubbard, science fiction writer and founder of scientology
- John F. Kennedy, commanding officer of motor torpedo boat PT-109 and 35th President of the United States
- Bob Kerrey, Navy SEAL Medal of Honor recipient and U.S. Senator
- Harvey Milk, gay rights activist and member of the San Francisco Board of Supervisors
- Thomas R. Norris, Navy SEAL and Medal of Honor recipient
- David Robinson, U.S. Naval Academy (Class of 1987) and National Basketball Association (NBA) Hall of Fame player
- Potter Stewart, served in World War II as a member of the U.S. Naval Reserve aboard oil tankers, Associate Justice of the United States Supreme Court
- Madeline Swegle, U.S. Navy's first black female tactical jet pilot
- Malcolm Wilson, New York politician
- Douglas A. "Doug" Roberts in the 1960s TV series Mister Roberts
- John Wayne as "Rusty" in the 1945 film They Were Expendable
- H. Paynter Jr. in The Caine Mutiny
- Radar intercept officers Nick "Goose" Bradshaw (Anthony Edwards), Ron "Slider" Kerner (Rick Rossovich), and Marcus "Sundown" Williams (Clarence Gilyard) in the 1986 film Top Gun
- Attorneys Daniel Alistair Kaffee (Tom Cruise) and Sam Weinberg (Kevin Pollak) in the 1992 film A Few Good Men
- Bright Noa in Mobile Suit Gundam
- Tim O'Neill and Lonnie Henderson in seaQuest DSV
- Nick Holden (Tony Curtis) in the 1959 film Operation Petticoat
- Cathy Connors (Barbara Eden) and Danny Romano (Frankie Avalon) in the 1961 film Voyage to the Bottom of the Sea
- Meg Austin (Tracey Needham) and Bud Roberts (Patrick Labyorteaux) in the 1990s TV series JAG
- Felix Gaeta in Battlestar Galactica
- Joseph Tormolen in the episode "The Naked Time" of Star Trek; this was the only time in TOS the rank was shown or named
- Saavik in Star Trek II: The Wrath of Khan, Star Trek III: The Search for Spock, and Star Trek IV: The Voyage Home
- Reginald Barclay in Star Trek: The Next Generation
- Iroquois Pliskin in Metal Gear Solid 2. Solid Snake was disguised as this U.S. Navy SEAL.
- Tom Paris in Star Trek: Voyager
- Ezri Dax was promoted from Ensign to LTJG by Captain Benjamin Sisko in Star Trek: Deep Space Nine; Doctor Julian Bashir was also LTJG during the earlier seasons
- Fred Boynton (Chris Eigeman) in the 1994 film Barcelona
- Deborah Solomon (Cheryl Ladd) in Purple Hearts
- Julian Mintz in Legend of the Galactic Heroes
- Fred-104 in Halo 5: Guardians
- Malcolm Blanke MD in C.S. Forester's short story "Dr Blanke's First Command". In the US Navy Reserve.
- LeRoy Carpentor in McHales Navy,
- 10 USC 5501. Navy: grades above chief warrant officer, W–5
- 37 USC 201. Pay grades: assignment to; general rules
- Mallory, John A. (1914). Compiled Statutes of the United States 1913. 1. St. Paul: Wast Publishing Company. p. 1062.
- "U.S. Navy history of LTJG George H. W. Bush".
- "G.I. Jobs -April 2008". Archived from the original on 2006-03-10.