Captain (United States O-3)

In the United States Army, captain is a company grade officer rank, with the pay grade of O-3. It ranks above first lieutenant and below major. It is equivalent to the rank of lieutenant in the naval rank system. The insignia for the rank consists of two silver bars, with slight stylized differences between the Army/Air Force version and the Marine Corps version. Promotion to captain is governed by Department of Defense policies derived from the Defense Officer Personnel Management Act of 1980. DOPMA guidelines suggest 95% of first lieutenants should be promoted to captain after serving a minimum of two years at their present rank.

An Army and Marine captain generally commands company-sized units. When given such a command, they bear the title company commander. Captains also instruct at service schools and combat training centers and are often staff officers at the battalion level. Marine captains also serve as officer selection officers, commanding recruiting stations for commissioned officers.

An Air Force captain's authority varies by group assignment. In an operations group, senior captains may be flight commanders while more junior captains may be heads of departments. In the maintenance or logistics and mission support groups they are almost always flight commanders. In the medical group, captains usually have limited administrative and command responsibility as captain is frequently the entry level rank for most medical officers and dental officers.

In Army and Air Force medical units, captain is the entry-level rank for those possessing a medical degree, or a doctorate in a healthcare profession (including pharmacists, optometrists, veterinarians, and dentists, among others). In Army and Air Force Judge Advocate General corps, lawyers with a Juris Doctor degree and membership in the bar of at least one U.S. state or territory are appointed captains, or first lieutenants promotable upon completion of initial entry training.

MARSOCs fourteen man Marine Special Operations Teams (MSOT) and U.S. Army Special Forces Operational Detachments Alpha are commanded by a captain.