The Town of Fairfield is located in the north eastern corner of Sauk County, Wisconsin, in the triangle between Baraboo, Wisconsin Dells and Portage. It borders the Wisconsin River to the north.

The town has a total area of 35.6 square miles (92.2 km²), of which, 35.0 square miles (90.6 km²) of it is land and 0.6 square miles (1.6 km²) of it (1.74%) is water.

It is home to the International Crane Foundation, the Aldo Leopold Foundation and the Pine Island Savanna State Natural Area. The Town of Fairfield is predominately a farming community.