Peter R. Mansoor (born February 28, 1960) is a retired United States Army officer, military historian, and commentator on national security affairs in the media.

He is also the author of The GI Offensive in Europe: The Triumph of American Infantry Divisions, 1941–1945 (1999), which received the Society for Military History distinguished book award in 2000.

He is the valedictorian of the class of 1978 of Mira Loma High School in Sacramento, California [2] Commissioned as a second lieutenant in May 1982, Mansoor served in a variety of command and staff assignments, including postings with the 3rd Armored Cavalry Regiment at Fort Bliss, Texas; the 11th Armored Cavalry Regiment in Bad Hersfeld and Fulda, Germany; and the 11th Armored Cavalry Regiment (Opposing Forces) at the National Training Center at Fort Irwin, California.

He commanded the 1st Squadron, 10th Cavalry and served as operations officer (G-3) of the 4th Infantry Division (Mechanized) at Fort Hood, Texas.

In the fall of 2006 he served on the so-called "Council of Colonels," a task force of senior officers created by the Joint Chiefs of Staff that reexamined the strategy for the war in Iraq.

[5] During its deliberations, Mansoor advocated sending additional troops to Iraq as part of the strategy eventually known as "the Surge," albeit at a lower strength level than the option preferred by then-Colonel H. R. McMaster, another member of the Council.