McKinsey & Company is a global American multinational strategy and management consulting firm headquartered in New York. Founded in 1926 by James O. McKinsey, initially as an accounting and management firm in Chicago, it pioneered the application of accounting principles to management practices, emphasizing budgeting, financial planning, and organizational efficiency. After James McKinsey's death in 1937, the firm restructured and, in 1939, separated from its accounting division. Under Marvin Bower's leadership, McKinsey established core principles of professionalism, client focus, and knowledge dissemination, transforming into a leading management consultancy known for rigorous analytical approaches, influential research, and extensive training programs. The firm incorporated as a private corporation in 1956, maintaining a partnership-like governance with elected managing directors, and opened its first international office in London in 1959.

Today, McKinsey is the oldest and largest of the top management consultancies known as "MBB" (McKinsey, Bain, BCG), employing over 30,000 people across more than 100 offices worldwide. It serves a broad clientele of corporations, governments, and non-governmental organizations, including Fortune 500 companies, offering advisory services in strategy, operations, digital transformation, sustainability, and more, across diverse industries such as finance, healthcare, technology, and consumer goods. The firm is recognized for investments in emerging technologies, including AI through divisions like QuantumBlack, and tools like Lilli. McKinsey’s organizational structure limits ownership to active members with individual share caps, fostering an egalitarian culture and significant influence in global business and policy networks. Throughout its history, leaders like Fred Gluck and Rajat Gupta expanded the firm's sector and functional practices and global presence. Despite its reputation as a trusted advisor to global leaders, McKinsey has faced controversies related to ethical concerns and settlements linked to its consulting work in areas such as the opioid crisis. The firm continues adapting by upskilling its workforce and developing AI capabilities to meet modern consulting challenges.