Jefferson Township is one of thirteen townships in Washington County, Indiana, United States. As of the 2020 census, its population was 830.

Historical population

Census	Pop.	Note	%±
1890	1,448		—
1900	1,450		0.1%
1910	1,240		−14.5%
1920	1,047		−15.6%
1930	852		−18.6%
1940	932		9.4%
1950	684		−26.6%
1960	698		2.0%
1970	728		4.3%
1980	836		14.8%
1990	944		12.9%
2000	841		−10.9%
2010	920		9.4%
2020	830		−9.8%
Source: US Decennial Census

According to the 2010 census, the township has a total area of 48.74 square miles (126.2 km), of which 48.1 square miles (125 km) (or 98.69%) is land and 0.64 square miles (1.7 km) (or 1.31%) is water.

• Haleysbury at 38°44′31″N 86°09′03″W / 38.741999°N 86.150814°W / 38.741999; -86.150814
• McKinley at 38°44′41″N 86°12′38″W / 38.744777°N 86.210538°W / 38.744777; -86.210538
• Prowsville at 38°40′48″N 86°12′06″W / 38.680056°N 86.201649°W / 38.680056; -86.201649
• Rush Creek Valley at 38°41′43″N 86°10′14″W / 38.695333°N 86.170537°W / 38.695333; -86.170537

(This list is based on USGS data and may include former settlements.)

• Carr Township, Jackson County (north)
• Driftwood Township, Jackson County (northeast)
• Monroe Township (east)
• Washington Township (southeast)
• Vernon Township (southwest)
• Brown Township (west)

The township contains these four cemeteries: Covenanter, Pollock, Thompson and Wheeler.

• John Hays Lake

• Salem Community Schools

• Indiana's 9th congressional district
• State House District 62
• State Senate District 44

• United States Census Bureau 2007 TIGER/Line Shapefiles
• United States Board on Geographic Names (GNIS)
• IndianaMap

• Indiana Township Association
• United Township Association of Indiana