Fairfield Township is a civil township of Lenawee County in the U.S. state of Michigan. As of the 2000 census, the township population was 1,756.
According to the United States Census Bureau, the township has a total area of 42.0 square miles (108.7 km²), all land.
As of the census of 2000, there were 1,756 people, 621 households, and 481 families residing in the township. The population density was 41.8 per square mile (16.2/km²). There were 666 housing units at an average density of 15.9 per square mile (6.1/km²). The racial makeup of the township was 97.49% White, 0.11% African American, 0.57% Native American, 0.06% Asian, 0.63% from other races, and 1.14% from two or more races. Hispanic or Latino of any race were 3.87% of the population.