The 33rd Massachusetts Volunteer Infantry was an infantry regiment that served in the Union Army during the American Civil War.

[1] The 33rd Regiment Massachusetts Infantry was organized at Springfield, Massachusetts and mustered in for a three-year enlistment on August 6, 1862 under the command of Colonel Adin B.

[2] The regiment was attached to Military District of Washington to October 1862.

3rd Brigade, 3rd Division, XX Corps, Army of the Cumberland, to June 1865.

[1] The 33rd Massachusetts Infantry mustered out of service on June 11, 1865 and was discharged July 2, 1865.

Brandy Station and Beverly Ford June 9.

March along line of Nashville & Chattanooga Railroad to Lookout Valley, Tenn., October 25–28.

Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church, and Allatoona Hills May 25-June 5.

Operations about Marietta and against Kennesaw Mountain June 10-July 2.

Ruff's Station or Smyrna Camp Ground July 4.

Duty as division train guard July 17 to August 27.

Operations at Chattahoochie River Bridge August 26-September 2.

Skirmish, Raleigh Road, near Fayetteville, N.C., March 14.