Captain ( United States O - 6 ) In the United States Navy and United States Coast Guard , captain is the senior - most commissioned officer rank below that of flag officer ( i . e . , admiral s ) . Reflecting its nautical heritage , it also sometimes used as a military " title " by more junior officers who are serving as the commanding officer ( CO ) of a commissioned vessel of the Navy or Coast Guard of patrol boat size or greater . ( " see rank vs . title " ) U . S . Navy . In the United States Navy , captain ( abbreviated CAPT ) is a senior officer rank , with the pay grade of O - 6 . It ranks above commander and below rear admiral ( lower half ) . It is equivalent to the rank of colonel in the other uniformed services . Promotion to captain is governed by Department of Defense policies derived from the Defense Officer Personnel Management Act ( DOPMA ) of 1980 . DOPMA guidelines suggest that no more than 50 % of eligible commanders should be promoted to captain after serving a minimum of three years at their present rank and after attaining 21 – 23 years of cumulative commissioned service . Navy captains with sea commands in the surface warfare officer community generally command ships of cruiser size or larger . The more senior the officer , the larger the ship . Others may hold command as commodore s of destroyer squadrons ( DESRON ) consisting of multiple destroyer s and frigate s . In the submarine community , a captain will typically command a ballistic - missile submarine ( SSBN ) , or a squadron of attack submarines ( SSN ) . Like their surface warfare counterparts , they may also serve as commodores of submarine squadrons ( SUBRON ) , commanding a group of submarines . In Naval Aviation , captains with sea commands are Naval Aviator s or Naval Flight Officer s who are commanding officers of aircraft carrier s or air - capable amphibious assault ships , commanders of carrier air wing s ( CAG ) , or commodores of functional or " type " air wings or air groups . A smaller cohort outside of sea commands may also serve as astronauts on loan to the National Aeronautics and Space Administration ( NASA ) . In the Naval Special Warfare " Sea Air Land " ( SEAL ) community , captains with sea commands are typically commodores in command of Naval Special Warfare Groups ( NAVSPECWARGRU ) . In contrast , commanders of aircraft carrier strike groups ( CSG ) and expeditionary strike groups ( ESG ) are normally rear admiral s , while subordinate destroyer squadron commodores , amphibious squadron commodores , carrier air wing commanders and the individual ship commanding officers within the strike group are of captain rank or lower . In rare instances , the carrier air wing commander may be a Marine Corps colonel who is a Naval Aviator or Naval Flight Officer ; while in the expeditionary strike group , the Marine Expeditionary Unit ( MEU ) commanding officer will always be a Marine Corps colonel . Adding to the confusion , all commanding officers of Navy ships and submarines are called " captain " regardless of actual rank . Navy captains who are line officer s may also fill important senior staff positions as Chiefs of Staff or Executive Assistants to flag officer s , or have shore based command assignments , such as commanding officers of naval bases , naval stations , naval air stations , naval air facilities , naval support activities , logistics groups , specialized centers or schools , or commanders of test wings or training air wings . They may also occupy senior leadership positions on fleet staffs , naval component commands staffs , the staffs of the joint Unified Combatant Command s , the staff of the Chief of Naval Operations ( OPNAV ) , or the Joint Staff . As opposed to line officer captains , staff corps captains will command facilities and organizations appropriate to their designators , such as naval hospitals commanded by medical corps , dental corps , medical service corps or nurse corps officers ; supply centers by supply corps officers ; or trial service offices commanded by judge advocate general corps officers . U . S . Coast Guard . The United States Coast Guard also uses the naval rank system . A Coast Guard captain ranks above a commander and below rear admiral ( lower half ) . The sleeve and shoulder board insignia are similar to the Navy insignia , with a lighter shade of blue with a gold USCG shield above the stripes . Coast Guard captains follow career paths very similar to their Navy counterparts , with seagoing officers typically commanding large maritime security cutter s or high endurance cutter s and aviators commanding coast guard air stations . Coast Guard captains will also command all types of major Coast Guard shore installations and activities , as well as serve as chiefs of staff for Coast Guard flag officers . The Coast Guard has no staff corps officers . U . S . Public Health Service and NOAA . In the United States Public Health Service , and in the National Oceanic and Atmospheric Administration Commissioned Corps , captains are senior non - combatant officers that serve as directors or ranking supervisors in their respective uniformed service corps . Seagoing NOAA captains will command certain NOAA ships , while NOAA aviators will command NOAA flight operations activities . USPHS rapid deployment force teams , containing 105 PHS physicians , nurses , and other medical professionals , are exclusively commanded by captains . U . S . Maritime Service . Although it exists largely as a maritime training organization , the United States Maritime Service also uses the rank of captain . Even though the Maritime Service is an auxiliary service , the grade is appointed by the President via the Secretary of Transportation , making it a federally recognized rank with corresponding paygrade of O - 6 .