The United States Army Ordnance Corps, formerly the United States Army Ordnance Department, is a sustainment branch of the United States Army, headquartered at Fort Lee, Virginia. The broad mission of the Ordnance Corps is to supply Army combat units with weapons and ammunition, including at times, their procurements and maintenance. Along with the Quartermaster Corps and Transportation Corps, it forms a critical component of the U.S. Army logistics system.

The U.S. Army Ordnance Corps mission is to support the development, production, acquisition, and sustainment of weapon systems, ammunition, missiles, electronics, and ground mobility materiel during peace and war to provide combat power to the U.S. Army. The officer in charge of the branch for doctrine, training, and professional development purposes is the Chief of Ordnance. The current Chief of Ordnance is Brigadier General Robin Montgomery.

During the colonial era in America, each colony was responsible for its own supply of ordnance material and its own personnel to supervise it. The first written record of an ordnance officer in British colonial America was Samuel Sharpe in the Massachusetts Bay Colony appointed in 1629 as Master Gunner of Ordnance. By 1645, the Massachusetts Bay Colony had a permanent Surveyor of Ordnance officer. By the time of the American Revolution, every colony had their own ordnance organization responsible for the procurement, distribution, supply, storage, and maintenance of munitions for the colony.

In July 1775, Ezekiel Cheever was appointed by General George Washington as Commissary of Artillery Stores, soon to be called Commissary of Military Stores with Major General Henry Knox, the Chief of Artillery. He was the civilian in charge of ordnance support for Washington's army in the field. By the end of the American Revolution, every brigade had ordnance personnel, usually civilian, providing munitions support to the soldiers in the field.

In 1776, the Board of War and Ordnance was established to oversee the conduct of the war. This board selected Benjamin Flower to be the Commissary General of Military Stores. Benjamin Flower was given the rank of Colonel and served in that capacity throughout the American Revolution. The Commissary General of Military Stores was an echelon above the Commissary of Military Stores in the field. His responsibility was to recruit and train artificers, establish ordnance facilities, and to distribute arms and ammunition to the army in the field. In 1777, a powder magazine was established at Carlisle, Pennsylvania and a foundry at Springfield, Massachusetts.

In the early years of the 19th century, the ordnance profession played a key role in the burgeoning industrial revolution in America. In 1794, President Washington established the two federal armories; the Springfield Armory in Massachusetts and the Harpers Ferry Armory in Virginia. At these locations, early developments and innovations striving towards interchangeable parts were achieved. Inventors such as Thomas Blanchard, Simeon North, John Hall, and Eli Whitney would perfect the methods and means for mass production. Growing out of the technical innovations of the arms industry, these methods would be widely adopted by American industry by the middle of the 19th century, establishing what has become known as the American system of manufacturing.

On 14 May 1812, as part of the preparation for the War of 1812, Congress established the Ordnance Department. It was responsible for arms and ammunition production, acquisition, distribution, and storage or ordnance materiel for the U.S. Army. The act also created a new position, the Commissary General of Ordnance. Colonel Decius Wadsworth, former Superintendent of the U.S. Military Academy at West Point, was chosen as the Commissary General of Ordnance. The act also directed the new Commissary General of Ordnance, soon renamed to Chief of Ordnance, to "enlist artisans and laborers to direct the inspection and proof of all cannon and small arms to direct the construction of gun carriages equipments implements and ammunition to make estimates and contracts for and purchases of ordnance supplies and stores and to issue them to the army to exact from armories and arsenals quarterly returns of property and to receive from all responsible officers reports of damages to ordnance materiel to establish ordnance depots to prepare regulations for the government of the Ordnance Department and forms of returns and reports".

Wadsworth also took great care in establishing and supervising the training of officers who would join the Ordnance Department. Coming from West Point, these officers, such as Alfred Mordecai and George Bomford, were highly trained in mechanical and chemical engineering and were among the highest ranking of graduating cadets from West Point. These new ordnance officers were usually detailed to the Springfield or Harpers Ferry Armory, or to one of the various arsenals across the growing country, to conduct scientific and industrial experiments in metallurgy, chemistry, or one of the allied engineering fields.