A quartermaster, in the United States Army, is a soldier or unit which specializes in supplying and provisioning troops in the field.

In the United States Navy, the term is used quite differently. It refers to a petty officer who specializes in navigation.

In the British Army, the Quartermaster (QM) is the officer in a battalion or regiment responsible for supply. By longstanding tradition, he or she is always commissioned from the ranks (and is usually a former Regimental Sergeant Major) and holds the rank of captain or major. Some units also have a Technical Quartermaster, who is in charge of technical stores. The Quartermaster is assisted by the Regimental Quartermaster Sergeant (RQMS) and a staff of storemen. The QM, RQMS and storemen are drawn from the regiment or corps in which they work, not from the Royal Logistic Corps, which is responsible for issuing and transporting supplies to them.

Until 1813, the Quartermaster was the senior NCO in a British cavalry troop. In that year, the position was replaced by the new appointment of Troop Sergeant Major, the cavalry adopting commissioned, regimental Quartermasters as described above.