Joseph Kugler (15 January 1867 - 10 June 1946) was a German Roman Catholic professed religious of the Brothers Hospitallers of Saint John of God. Kugler entered the congregation in 1893 and assumed his religious name of "Eustachius" upon admittance. Kugler came into direct contact with the Gestapo during World War II and came to their attention due to being an outspoken critic of Adolf Hitler and the Nazi regime. He also opposed their approval of euthanasia of the ill and old and their anti-Christian policies.