An officer of one-star rank is a senior commander in many of the armed services holding a rank described by the NATO code of OF-6. The term is also used by some armed forces which are not NATO members. Typically, one-star officers hold the rank of commodore, flotilla admiral, brigadier general, brigadier, or in the case of those air forces with a separate rank structure, air commodore.
Officers of one-star rank are either the most junior of the flag, general and air officer ranks, or are not considered to hold the distinction at all. Specifically, in many navies, one-star officers are not considered to be flag officers, although this is not always the case. The army and air force rank of brigadier general is, by definition, a general officer rank. However, the equivalent rank of brigadier is usually not designated as a general officer. The air force rank of air commodore is always considered to be an air-officer rank.
Australian one-star ranks
- Commodore (Royal Australian Navy one-star rank)
- Brigadier (Australian Army one-star rank)
- Air commodore (Royal Australian Air Force one-star rank)
Canadian one–maple-leaf ranks
- Commodore (Royal Canadian Navy one-star-equivalent rank)
- Brigadier-general/brigadier-général (Canadian Army and Royal Canadian Air Force one-star-equivalent rank)
The maple leaf appears with St. Edward's crown and crossed sabre and baton.
Indian one-star ranks
- Air commodore (Indian Air Force one-star rank)
- Brigadier (Indian Army one-star rank)
- Commodore (Indian Navy one-star rank)
Pakistani one-star ranks
- Deputy inspector general of police (Pakistan Police one-star rank)
- Air commodore (Pakistan Air Force one-star rank)
- Brigadier (Pakistan Army one-star rank)
- Commodore (Pakistan Navy one-star rank)
British one-star ranks
- Commodore (Royal Navy one-star rank)
- Brigadier (British Army and Royal Marines one-star rank)
- Air commodore (Royal Air Force one-star rank)
US one-star ranks
- Rear admiral (lower half) (United States Navy, Coast Guard, Public Health Service Commissioned Corps and National Oceanic and Atmospheric Administration Commissioned Corps one-star rank)
- Brigadier general (United States Army, Marines and Air Force one-star rank)
In the modern naval services of Belgium, Denmark, Finland, Germany and Sweden, the one-star rank is flotilla admiral.