The Basilica of St. Mary of the Assumption is a minor basilica of the Catholic Church located in Lancaster, Ohio, United States, and a parish church of the Diocese of Columbus. The parish was founded in 1818 and the current church building was completed in 1864. When the Holy See declared the church a minor basilica in 2022, it became the 91st in the United States, the seventh in Ohio, and the first in the Diocese of Columbus.