Karl Paul Reinhold Niebuhr (June 21, 1892 – June 1, 1971) was an American theologian. A Protestant, he is best known for his study of the task of relating the Christian faith to the realities of modern politics and diplomacy. He was an important contributor to modern "just war" thinking.
Niebuhr was born in Wright City, Missouri, USA, son of German Evangelical pastor Gustav Niebuhr and his wife. Reinhold had a younger brother Helmut Richard Niebuhr. Both sons decided to follow in their father's footsteps and enter the ministry. Reinhold Niebuhr attended Elmhurst College in Illinois and graduated in 1910. He then studied at Eden Theological Seminary in Webster Groves, Missouri. Finally, Niebuhr attended Yale University, where he earned his Bachelor of Divinity Degree in 1914 and was a member of Alpha Sigma Phi Fraternity. In 1915, Niebuhr was ordained a pastor.
The German Evangelical mission board sent Niebuhr to serve in Detroit, Michigan. The congregation numbered sixty-five on his arrival and grew to nearly 700 by the time he left in 1928. The increase reflected the tremendous growth of population attracted to jobs in the booming automobile industry.
During his pastorate, Niebuhr was troubled by the demoralizing effects of industrialism on workers. He became an outspoken critic of Henry Ford and allowed union organizers to use his pulpit to expound their message of workers' rights. Niebuhr documented inhumane conditions created by the assembly lines and erratic employment practices.