Gregory Baum (1923-2017) was a Canadian theologian, philosopher, and professor, born in Germany. He was an influential figure in liberation theology and ecumenical dialogue. Ordained a Catholic priest, he later secularized and married. He taught at the University of St. Michael's College in Toronto and later at McGill University in Montreal. He was an important observer of the Second Vatican Council and wrote extensively on social justice, political theology, and the relationship between faith and society, advocating for a Christianity committed to social criticism and liberation.