Klemens von Ketteler (1811-1877) was a German bishop known for his advocacy of social justice and workers' rights during the Industrial Revolution. He served as the Bishop of Mainz and was a prominent figure in the Catholic Church, emphasizing the importance of addressing the needs of the working class. His writings and speeches highlighted the struggles faced by laborers and called for reforms to improve their conditions. Ketteler is often associated with the development of Catholic social teaching, which seeks to apply the principles of Christianity to social, economic, and political issues. His work laid the groundwork for later social encyclicals, including Rerum Novarum, which addressed the rights of workers and the responsibilities of employers.