The 51st Regiment Illinois Volunteer Infantry was an infantry regiment that served in the Union Army during the American Civil War.

The 51st Illinois Infantry was organized at Chicago, Illinois and mustered into Federal service on December 24, 1861.

The regiment was mustered out on September 25, 1865.

The regiment suffered 9 officers and 106 enlisted men who were killed in action or mortally wounded and 1 officer and 134 enlisted men who died of disease, for a total of 250 fatalities.

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