Michael P. Walsh (August 25, 1838 - April 2, 1919) was an American printer and labor union activist from Milwaukee, Wisconsin who held various local elected offices, as well as serving two terms as a member of the Wisconsin State Assembly from Milwaukee, initially as the nominee of the Milwaukee Trades Assembly, a labor federation which was also an antecedent to that state's Union Labor Party; but then was re-elected as a Democrat.
Walsh was born in Castlebar, County Mayo, Ireland on August 25, 1838; came to Wisconsin in about the year 1842 with his family and settled at Milwaukee, where he received a common school education, beginning his printing education as an apprentice printer in 1851 at the Milwaukee Sentinel. He left Milwaukee in 1859, and later described himself with "has lived and worked in all the principal cities of the country."
He joined the Union Army as a private in Company E of the 49th New York Volunteer Infantry in June, 1861, rising to orderly sergeant. With the Army of the Potomac his unit participated in battles which included Young's Mill, Yorktown, Williamsburg, Mechanicsville, Fair Oaks, Gaines's Mill, Savage's Station, Malvern Hill, Second Bull Run, South Mountain, Antietam, Fredericksburg, Williamsport, Gettysburg, Mine Run, Wilderness, Cold Harbor, Petersburg and others. Walsh was taken prisoner during operations against the Welden Railroad shortly prior to the expiration of his term of enlistment and was a prisoner at Belle Isle, Libby Prison, Andersonville, Savannah, Castle Pinckney and , before being exchanged and returned to Annapolis, Indiana, where he was honorably discharged May 5, 1865. At some point after this, he spent eight years working at the Wisconsin State Journal in Madison.