Lancaster Township is one of ten townships in Jefferson County, Indiana, United States. As of the 2020 census, its population was 1,494 (down from 1,511 at 2010) and it contained 610 housing units.
Eleutherian College and the Lyman and Asenath Hoyt House are listed on the National Register of Historic Places.
According to the 2010 census, the township has a total area of , of which (or 99.84%) is land and (or 0.16%) is water. The streams of Middle Fork Creek and Turkey Branch run through this township.
The township contains five cemeteries: Bland, Clashman, College Hill, Nelson and Ogden.
It is in the Madison Consolidated Schools school district.
The zoned MCS elementary school for part of the township is Anderson Elementary School, while another part is zoned to Deputy Elementary School. The zoned secondary schools of the Madison district are Madison Junior High School and Madison Consolidated High School.