The 18th Wisconsin Infantry Regiment was a volunteer infantry regiment that served in the Union Army in the western theater of the American Civil War.

A large portion of the regiment was captured in their first battle, at Shiloh, but they went on to participate in the Vicksburg Campaign, and Sherman's campaigns in Georgia and the Carolinas.

For much of the war, the regiment was commanded by Gabriel Bouck, who would later become a U.S. congressman and speaker of the Wisconsin State Assembly.

The regiment was mustered out on July 18, 1865, at Louisville, Kentucky.

The 18th Wisconsin suffered 4 officers and 52 enlisted men killed in action or who later died of their wounds, plus another 2 officers and 167 enlisted men who died of disease, for a total of 225 fatalities.