The 90th Regiment Illinois Volunteer Infantry was an infantry regiment that served in the Union Army during the American Civil War.

On two occasions, the unit included a disguised woman (Frances Elizabeth Quinn) in its ranks.

The first time she was discovered and dismissed within a month by Colonel Tomothy O'Meara.

The regiment suffered 2 officers and 58 enlisted men who were killed in action or who died of their wounds and 1 officer and 87 enlisted men who died of disease, for a total of 148 fatalities.

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