Brigadier general (Brig. Gen.) is a senior rank in the armed forces. It is the lowest ranking general officer in some countries, usually sitting between the ranks of colonel and major general. When appointed to a field command, a brigadier general is typically in command of a brigade consisting of around 4,000 troops (four battalions). In some countries a brigadier general is informally designated as a one-star general (OF-6).
In some countries, this rank is given the name of brigadier, which is often considered not to be a general-officer rank, but is usually equivalent to brigadier general in the armies of nations that use the rank.
The rank can be traced back to the militaries of Europe where a brigadier general, or simply a brigadier, would command a brigade in the field. The rank name général de brigade, (which translates as "brigade general"), was first used in the French revolutionary armies.
In the first quarter of the 20th century, British and Commonwealth armies used the rank of brigadier general as a temporary appointment, or as an honorary appointment on retirement; in the 1920s this practice changed to the use of brigadier, which was not classed as a general officer.
This gallery displays Air Force brigadier general insignia if they are different from the Army brigadier general insignia. (They usually are.)
Note that in many Commonwealth countries, the equivalent air force rank is Air Commodore (and in the Netherlands, it is simply Commodore).