In 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 Corps, lieutenant, junior grade (LTJG) is a junior officer, with the pay grade of O-2. Lieutenant, junior grade ranks above ensign and below lieutenant. Lieutenant, junior grade is equivalent to a First Lieutenant in the other uniformed services.
Until achieving the rank of Commander, it is customary to address junior naval officers as "Mister." For example, LTJG Roberts might be addressed as "Mister Roberts," or as "Lieutenant Roberts."
The time for promotion to LTJG is a minimum of two years after commissioning in the Navy or eighteen months in the Coast Guard.
The equivalent rank in the United States Army, United States Marine Corps and United States Air Force is first lieutenant. In the Royal Navy and the navies of many Commonwealth countries, the equivalent rank is Sub-Lieutenant.