Effner is an unincorporated community on the border of the U.S. states of Illinois and Indiana.

A post office was established at Effner in 1899, but closed shortly thereafter in 1901.

Most of Effner lies along the eastern edge of Sheldon Township in Iroquois County, Illinois; the local grain elevators and the defunct railway station are across the border in Jefferson Township in Newton County, Indiana.

A line of the Toledo, Peoria and Western Railway connecting Sheldon and Kentland passes through town just south of the highway.

This Iroquois County, Illinois location article is a stub.