1LT

1LT, short for First Lieutenant, is a commissioned officer rank used by the United States Army, Air Force, and Marine Corps, as well as in some other armed forces. It sits above Second Lieutenant (O-1) and below Captain (O-3). The insignia is a single silver bar, and officers at this rank hold pay grade O-2. In practice, 1LTs are considered junior officers with responsibility for leading or supporting mid-level units and missions.

In the Army and Marine Corps, a 1LT typically serves as a platoon leader, commanding a platoon of 16–44 soldiers, or as the executive officer of a company or troop. They may also fill staff roles at the battalion or brigade level or serve in specialized positions depending on branch, career field, and unit needs. In the Air Force, a 1LT may perform roles such as flight lead, deputy operations officer, or other mid-level leadership and staff assignments. Duties vary widely by branch, unit, and individual experience.

Promotion to 1LT usually follows promotion from 2LT after about 18–24 months of service, contingent on satisfactory performance and successful completion of required leadership and training standards. Advancement to Captain (O-3) depends on time in service, performance, and selection by promotion boards.

Historically, the First Lieutenant rank has existed in various forms for centuries and remains one of the standard junior officer ranks in contemporary U.S. military services. The term and abbreviation 1LT are widely used in official and informal writing to denote this rank.