Commodore ( Royal Navy ) Commodore ( Cdre ) is a rank of the Royal Navy above Captain and below Rear Admiral . It has a NATO ranking code of OF - 6 . The rank is equivalent to Brigadier in the British Army and Royal Marines and to Air Commodore in the Royal Air Force . History . The appointment of Commodore dates to the mid - 17th century : it was first used in the time of William III . There was a need for officers to command squadron s , but it was not deemed desirable to create new admirals ( as Post - Captain s were promoted to Rear - Admiral in order of seniority ) . Captains assigned squadron command were given the title of Commodore , but it was not an actual rank . The officer so designated kept his place on the list of Captains . In 1748 it was established that Captains serving as Commodores were equal to Brigadier - General s in the Army . Commodores could revert to the rank of Captain at the end of their posting ( and Captains could be promoted directly to Rear - Admiral without ever having served as a Commodore ) . The Royal Navy Commodore was eventually split into two classes . Those of the first class had a Captain under them to command their ship and were allocated one - eighth of all prize money earned by ships under their command . Those of the second class commanded their own ship as well as the squadron . In 1783 , Commodores of the first class were allowed to wear the uniform of a Rear - Admiral , a distinction which continued with some variation until the two classes of Commodore were consolidated in 1958 . By the 20th century , Commodores did not just command seagoing units ( the naval barracks in the three main naval bases of Devonport , Portsmouth and Chatham were all commanded by Commodores , for instance ) and the appointment of Commodore could also be held by specialist officers in certain positions as well as by line officers . The Royal Air Force rank of air commodore was derived from the Royal Navy rank of commodore in 1919 . In 1996 , Commodore was made a substantive rank in the Royal Navy . It had previously been an appointment , with the holder a Captain , reverting to the status of Captain at the end of the appointment . Insignia . Commodores First Class , while wearing the sleeve stripes of a Rear - Admiral , had gold lace - covered epaulette s with a crown , two stars and an anchor ( also worn by other Commodores but only with formal uniforms ) . They flew a swallow - tailed pennant with the St George ' s cross , but without the disc that appeared on the pennant of a Second Class Commodore . Commodores Second Class wore a single 1 . 75 inch - wide row of lace below a ring ( known in naval regulations as a curl ) measuring 1 . 75 inches in diameter on both sleeve and shoulder - board . Their uniforms were otherwise the same as for Captains . Modern Commodores wear the insignia previously worn by Commodores Second Class . Equivalent naval ranks . Some Commonwealth countries have replaced Commodore with an equivalent flag rank . The correct sleeve insignia for such a rank is a single 1 . 75 inch - wide row of gold lace below a gold lace curl with a diameter of 2 inches . The correct shoulder - board insignia comprises a crown ( or national emblem for republics ) with a crossed sword and baton on a gold lace - covered shoulder - board , however , there is some variation due to misconceptions about the status of stars in Commonwealth - style rank insignia . The rest of the uniform is identical to that of a Rear - Admiral . < br >