The 101st Infantry Regiment was a formation of the United States Army, Massachusetts Army National Guard. Its history dates back to the American Civil War, and continues to the Spanish–American War, World War I, and World War II before being deactivated in 1993. The spirit of this unit and its history lives on in the modern 26th Infantry Brigade Combat Team of the Massachusetts Army National Guard.

The Massachusetts National Guard is the National Guard component for the Commonwealth of Massachusetts. Founded as the Massachusetts Bay Colonial Militia on December 13, 1636, it contains the oldest units in the United States Army. What is today's Massachusetts National Guard evolved through many different forms. Originally founded as a defensive militia for Puritan colonists in the Massachusetts Bay Colony, the militia evolved into a highly organized and armed fighting force. The Massachusetts militia served as a central organ of the New England revolutionary fighting force during the early American Revolution and a major component in the Continental Army under George Washington.