The 29th Regiment Massachusetts Volunteer Infantry was an infantry regiment in the Union army of the United States during the American Civil War. The regiment was organized in December 1861 when three new companies were attached to a battalion of seven Massachusetts companies that had been in active service since May 1861. These seven companies had been recruited to fill out the 3rd Massachusetts and 4th Massachusetts regiments and had signed on for three years of service. When the 3rd and 4th Massachusetts were mustered out in July 1861, the seven companies that had signed on for three years were grouped together to form a battalion known as the Massachusetts Battalion. Finally, in December 1861, three more companies were added to their roster to form a full regiment and the unit was desi