Union Township is one of eleven townships in Randolph County, Indiana, which contains the towns of Modoc and Losantville. As of the 2020 census, its population was 1,965 (down from 2,142 at 2010) and it contained 902 housing units.

Union Township was established on 1 January 1951 from the merger of Nettle Creek Township and West River Township.

Confusingly, another Union Township was proposed in Randolph County in 1838. This Union Township was either short lived or was never formed. It would have consisted of the northern half of the existing West River Township

According to the 2010 census, the township has a total area of 71.65 square miles (185.6 km), of which 71.52 square miles (185.2 km) (or 99.82%) is land and 0.13 square miles (0.34 km) (or 0.18%) is water.

• Losantville
• Modoc

• Huntsville at 40°04′16″N 85°04′20″W / 40.0711567°N 85.0721876°W / 40.0711567; -85.0721876
• Scott Corner at 40°05′31″N 85°07′37″W / 40.0919897°N 85.1269105°W / 40.0919897; -85.1269105
• Unionport at 40°07′15″N 85°05′47″W / 40.1208783°N 85.0963553°W / 40.1208783; -85.0963553

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

Union Township has nine cemeteries:

• Buena Vista Cemetery
• Huntsville Cemetery
• Little Creek Cemetery
• Nettle Creek Baptist Cemetery
• Riverside Cemetery
• Salem Cemetery
• Scott Cemetery
• Union Baptist Cemetery
• Union Chapel Cemetery

• U.S. Route 36
• U.S. Route 35
• Indiana State Road 1

• Indiana Township Association
• United Township Association of Indiana