Kilian Caspar Flasch was a German-born prelate of the Roman Catholic Church who served as bishop of the Diocese of La Crosse in Wisconsin from 1881 until his death in 1891.

The Roman Catholic Diocese of La Crosse is a Latin Church diocese in west-central Wisconsin in the United States. The metropolitan for the diocese is the Archdiocese of Milwaukee. The mother church is the Cathedral of Saint Joseph the Workman in La Crosse.