This is a list of United States military units that participated in the Mexican–American War. The list includes regular U.S. Army, Navy, Marine Corps, and Revenue Marine Service units and ships as well as the units of the militia that various states recruited for the war. The commanding officer of each unit or ship is identified when there are references with content that aids identification. Dates are included when they are available in the references.

Regular U.S. Army regiments serving in Mexico from 1846 to 1848

Regiments of dragoons

Mounted riflemen

Regiments of artillery

Regiments of infantry

Regiments of infantry, 1847

Volunteer units serving in Mexico from 1846 to 1848

Alabama

Arkansas

California

Florida

Georgia

Illinois

Indiana

Iowa

The Mormon Battalion was recruited as a federal volunteer unit, not through the state of Iowa which was not created until December 1846. The Mormon Battalion was raised at the express invitation of President James K. Polk, not as part of any state or territorial requisition for troops. The contemporary official Army documents refer to the unit in the following ways; Prior to Allen recruiting the unit as, "Capt. Allen's Battalion of Volunteers". As the new unit was being recruited and mustered into service, its first commander, James Allen, signed official documents with the name he gave the unit, "Mormon Battalion", General Stephen Watts Kearny, in letters of reply to the unit used Allen's naming convention, calling it the "Battalion of Mormons" and "Mormon Battalion" P. St. George Cooke, commanding the battalion under orders from Gen Kearny used the name, "Mormon Battalion" when reporting troop strengths in California.

Kentucky

Louisiana

Maryland and the District of Columbia

Maine

Massachusetts

Michigan

Mississippi

Missouri

New Jersey

New York

North Carolina

Ohio

Pennsylvania

South Carolina

Tennessee

Texas

Virginia

Misc. volunteers

U.S. Navy squadrons serving in the war

Home Squadron

Pacific Squadron

U.S. Marine Corps

U.S. Revenue Marine