The 55th Illinois Volunteer Infantry Regiment was an infantry regiment that served in the Union Army during the American Civil War.

The 55th Illinois Infantry was organized at Camp Douglas, Chicago, Illinois and mustered into Federal service on October 31, 1861.

Training continued at Benton Barracks, Missouri.

The regiment suffered casualties including nine officers, 149 enlisted men who were killed in action, or mortally wounded, and two officers and 127 enlisted men who died of disease, for a total of 286 fatalities.

This article about a specific military unit of the American Civil War is a stub.