Bath Township is one of the twelve townships of Allen County, Ohio, United States. The 2020 census found 9,399 people in the unincorporated parts of the township, outside the city of Lima.

Allen County is a county located in the northwestern part of the U.S. state of Ohio. Its county seat and largest city is Lima. The county was created in 1820 and organized in 1831. The county is named in honor of Colonel John Allen, who was killed leading his men at the Battle of Frenchtown during the War of 1812.