Baker McKenzie is a multinational corporate law firm headquartered in Chicago. Founded in 1949, as Baker & McKenzie, it operates decentralized offices in 45 countries, and is best known for its cross-border trading and tax law expertise.

Co-founding partner Russell Baker, who had graduated from the University of Chicago Law School, opened his first practice, Baker & Simpson, with Dana Simpson, in Chicago in 1925. The firm provided legal services to the growing Mexican American community in Chicago, which would set a foundation for its global reach. Simpson retired in 1932. In 1949 Baker was joined by John McKenzie, a graduate from Loyola University Chicago School of Law, who helped further establish the international practice.

Baker McKenzie became the first multinational law firm in the world, beginning in 1955, after a lawyer in Venezuela contacted the firm, seeking to open a joint venture office in Caracas. Russell Baker's son, Donald, moved to Caracas to launch the satellite office. Within the next three years, offices were opened in Washington, D.C., Amsterdam, Brussels, Zürich, New York City and São Paulo. By 1978, Baker McKenzie had 26 offices in 20 countries. By 1990, the firm operated 49 offices on six continents, employing around 1500 attorneys, and generating $400 million in annual revenue.

In 1999, Christine Lagarde, the Paris managing partner and an antitrust and labor lawyer, was elected chair of the global executive committee, the first woman to lead Baker McKenzie, or a major international law firm; she was chair for five years. Legarde later became France's Minister of Finance and managing director of the International Monetary Fund.

In 2001, the firm employed 3,000 attorneys and garnered $1 billion in revenues. In 2005, 70 partners, and other legal staff, from the New York office of disbanding international firm Coudert Brothers joined Baker McKenzie.

In 2004, Baker McKenzie was the first major law firm to become a Swiss Verein. In October 2006, Unilever chose the firm to manage its global trademark portfolio, the largest in the world, with over 160,000 registrations, marking the first time a multinational company outsourced its trademark management to a law firm on such a large scale.

In July 2013, co-founding partner Russell Baker was named one of American Lawyer's top 50 innovators for pioneering ideas and initiatives that changed the world of BigLaw.

In August 2014, Baker McKenzie revealed it was the first law firm to record $2.5 billion in revenues since the 2008 financial crisis, and that it was also the largest firm in the world by headcount.