In the United States Armed Forces, a brigadier general is a one-star general officer in the United States Army, Marine Corps, Air Force, and Space Force.

A brigadier general ranks above a colonel and below a major general. The pay grade of brigadier general is O-7. It is equivalent to the rank of rear admiral (lower half) in the other United States uniformed services which use naval ranks. It is abbreviated as BG in the Army, BGen in the Marine Corps, and Brig Gen in the Air Force and Space Force.

The Civil Air Patrol also uses this grade for its National Vice Commander and some past National commanders.

The rank of brigadier general has existed in the U.S. military since the inception of the Continental Army in June 1775. To prevent mistakes in recognizing officers, a general order was issued on July 14, 1775, establishing that brigadier generals would wear a ribbon, worn across the breast, between coat and waistcoat, pink in color. Later, on June 18, 1780, it was prescribed that brigadier generals would instead wear a single silver star on each epaulette. At first, brigadier generals were infantry officers who commanded a brigade; however, over the course of the 19th and 20th centuries, the responsibilities of the rank expanded significantly.

During the period from March 16, 1802, to January 11, 1812, the rank of major general was abolished and brigadier general became the highest rank in the U.S. Army. Foreseeing the need for an expanded general staff in case of war, which seemed imminent, Congress restored the rank of major general in January 1812.

The insignia for a brigadier general is one silver star worn on the shoulder or collar, and has not changed since the creation of the rank two centuries ago. Since the Mexican–American War, however, the lower rank of colonel has been the normal rank appointed to command a brigade that is organic to a division (e.g., the 1st Brigade of the 94th Infantry Division, vice the 187th Infantry Brigade). While separate brigades (e.g. the 187th, commanded by then-BG William Westmoreland in Korea) were traditionally commanded by brigadier generals, this practice has ceased in recent history.

Today, an Army or Marine Corps "BG" or "BGen," respectively, typically serves as deputy commander to the commanding general of a division or division-sized units and assists in overseeing the planning and coordination of a mission. A Marine Expeditionary Brigade (MEB), as the medium capability (and sized) scalable Marine Air Ground Task Force (MAGTF) with up to 20,000 Marines, is normally commanded by a Marine BGen. An Air Force brigadier general typically commands a large wing or serves as the deputy commander for a NAF. Additionally, one-star officers of all services may serve as high-level staff officers in large military organizations.

U.S. law explicitly limits the total number of general officers who may be on active duty. The total number of active duty general officers is capped at 219 for the Army, 64 for the Marine Corps, 171 for the Air Force, and 21 for the Space Force. The President or Secretary of Defense may increase the number of slots for one branch, so long as they subtract an equal number from another. Some of these slots are reserved by statute.