Jefferson Township is one of twenty townships in Fayette County, Iowa, United States. As of the 2010 census, its population was 6,910.
According to the United States Census Bureau, Jefferson Township covers an area of 36.46 square miles (94.42 square kilometers); of this, 36.37 square miles (94.2 square kilometers, 99.77 percent) is land and 0.09 square miles (0.22 square kilometers, 0.23 percent) is water.
The township contains these three cemeteries: Oakdale, Otsego and Woodlawn.