Ernst & Young (doing business as EY) is a multinational professional services firm headquartered in London, England, United Kingdom. EY is one of the largest professional services firms in the world and is one of the "Big Four" accounting firms.
EY operates as a network of member firms which are separate legal entities in individual countries. It has 270,000 employees in over 700 offices around 150 countries in the world. It provides assurance (including financial audit), tax, consulting and advisory services to companies.
The firm dates back to 1849 with the founding of Harding & Pullein in England. The current firm was formed by a merger of Ernst & Whinney and Arthur Young & Co. in 1989. It was known as Ernst & Young until 2013 when it underwent a rebranding to EY. The acronym "EY" was already an informal name for the firm prior to its official adoption.
In 2018, Fortune magazine ranked EY 52nd on the 100 Best Companies to Work For list. In 2017, EY was the 9th largest privately owned organization in the United States.