William G. Parrett (born June 4, 1945) is an American businessman and senior manager who has served public, private, governmental, and state-owned clients worldwide.

[2][3] In May 2018, he stepped down from this role and was focussing on the position of President of UBS Americas Holding LLC.

Parrett graduated with an undergraduate degree (BBA) in accounting from St. Francis College, New York, in 1967.

[6] Parrett was the chairman of the board of the United States Council for International Business from April 2005 through March 2010.

[14] As a member of the boards of Kodak, Blackstone Group, and Thermo Fisher Scientific, he is required to publicly report his interests in those companies, amounting approximately to US$4 million, as of 2016.