John Collier (May 4, 1884 – May 8, 1968), a sociologist and writer, was an American social reformer and Native American advocate. He served as Commissioner for the Bureau of Indian Affairs in the President Franklin D. Roosevelt administration, from 1933 to 1945. He was chiefly responsible for the "Indian New Deal," especially the Indian Reorganization Act of 1934, through which he intended to reverse a long-standing policy of Cultural assimilation of Native Americans.