Jefferson Township is one of twelve townships in Jay County, Indiana, United States. As of the 2020 census, its population was 684 (down from 770 at 2010) and it contained 292 housing units.

Jefferson Township was organized in 1837.

According to the 2010 census, the township has a total area of 35.16 square miles (91.1 km), of which 35.13 square miles (91.0 km) (or 99.91%) is land and 0.03 square miles (0.078 km) (or 0.09%) is water. The streams of Bost Run, Como Run, Jeff Run, Jutte Run, New Mount Run and Vale Run run through this township.

• Como
• New Mount Pleasant
• Powers

• Greene Township (north)
• Wayne Township (northeast)
• Pike Township (east)
• Ward Township, Randolph County (southeast)
• Franklin Township, Randolph County (south)
• Green Township, Randolph County (southwest)
• Richland Township (west)
• Knox Township (northwest)

The township contains seven cemeteries: Bost, Flesher, New Mount Pleasant, Powers, Stephens, Stratton and Wentz.

• SR 67

• Windy P Ridge Airport

• "Jefferson Township, Jay County, Indiana". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved September 24, 2009.
• United States Census Bureau cartographic boundary files

• Indiana Township Association
• United Township Association of Indiana