The 20th Regiment Illinois Volunteer Infantry was an infantry regiment that served in the Union Army during the American Civil War.

The 20th Illinois Infantry was organized at Joliet, Illinois and mustered into Federal service on June 13, 1861, for a three-year enlistment.

The regiment was mustered out of service on July 16, 1865.

The regiment suffered 7 officers and 132 enlisted men who were killed in action or who died of their wounds and 1 officer and 191 enlisted men who died of disease, for a total of 331 fatalities.

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