James Oscar McKinsey (June 4, 1889 – November 30, 1937) was the founder of McKinsey & Company.
Management theory was still in its infancy when James O. McKinsey (or Mac, as he was known by friends and colleagues) founded the firm that bears his name in 1926. He had left his academic career as a professor of accounting at the University of Chicago Booth School of Business to build a firm that provided finance and budgeting services, but quickly gained a reputation for providing advice on organization and management issues.
Mac was determined to help senior management in American companies solve their most important business problems. In an era when "management engineers" were largely efficiency experts, Mac set out to enlarge the profession's scope by persuading clients that his young firm could not only help inefficient companies but also assist healthy companies in reorienting themselves to thrive in a turbulent business environment.