Sidney Township is one of thirteen townships in Fremont County, Iowa, United States. As of the 2010 census, its population was 1,741 and it contained 767 housing units.
As of the 2010 census, Sidney Township covered an area of ; of this, (99.78 percent) was land and (0.22 percent) was water.
The township contains Abshire Cemetery, Acord Cemetery, Benson Cemetery, Fremont County Cemetery, Grandview Cemetery, Hume Cemetery, Knox Cemetery, Lacy Cemetery, Parsley Cemetery, Rector Cemetery, Redd Cemetery and Sidney Cemetery.