Professor Bennis wrote more than 30 books on leadership, a subject that grabbed his attention early in life, when he led a platoon during World War II at the age of 19. As a consultant, Professor Bennis was sought out by generations of business leaders, among them Howard D. Schultz, the chief executive of Starbucks, who regarded him as a mentor. Presidents John F. Kennedy, Lyndon B. Johnson, Gerald R. Ford and Ronald Reagan all conferred with him. As an educator, he taught organizational studies at Harvard, Boston University and the M.I.T. Sloan School of Management. He enrolled at Antioch College in Ohio and earned a bachelor’s degree in 1951. Its innovative president, Douglas McGregor, a social psychologist, had taken him under his wing and recommended him to M.I.T. for postgraduate work. There he completed a doctorate in economics, studying under Paul A. Samuelson, Franco Modigliani and Robert M. Solow, all of whom were later awarded the Nobel in economic science. He joined U.S.C. in 1980 as a business professor. Professor Bennis’s first marriage, in 1962, to Clurie Williams, ended in divorce. He is survived by his wife, Dr. Grace Gabe, a physician he married in 1992; his children from his first marriage, Katherine, John and Will Bennis; his stepdaughters, Nina Freedman and Eden Steinberg; six grandchildren; and four step-grandchildren.