The 135th Illinois Infantry Regiment was an infantry regiment from Illinois that served in the Union Army between June 6 and September 28, 1864, during the American Civil War.

The regiment was organized at Mattoon, Illinois, with a strength of 852 men,[2] and mustered in for one-hundred-day service on June 6, 1864.

[3][4] On June 10, the regiment departed for Benton Barracks, Missouri, where they reported to General William Rosecrans.

[2][4] From there five companies of the regiment were stationed on the Iron Mountain railroad.

[2][4] During its service the regiment lost one man at Gasconade crossing and sixteen men to disease.