Whitney MacMillan is an American heir, businessman, philanthropist, and rancher with an estimated net worth of $5.3 billion as of April 2016, according to Forbes. He is #395 in the World Billionaires List (#344 in 2012), #131 in the United States, and #132 in the Forbes 400 List. With his net worth, he is the richest person in Minnesota. Born on September 25, 1929, he is the great-grandson of William G. Cargill, the founder of Cargill. He is the son of Cargill MacMillan Sr. He is a graduate of Yale University.

From 1976 to 1995, MacMillan is the CEO of Cargill and the last Cargill family member to serve as CEO. For over ten years of his tenure, the firm went from $10 billion to $33 billion. It became the largest grain company in the 1980's while outstripping its European rivals. It is now the largest private company in the U.S. with $134 billion in revenues during the 2012 fiscal year. Its earnings came from all areas of food production such as crops, cattle, commodity trading, and even risk management. He is one of the six secretive billionaire relatives who together still own a majority of the company. He is also a major shareholder of The Mosaic Company and serves as a director of the Western NIS Enterprise Fund.

As a philanthropist, Whitney MacMillan has served on the board of directors of the International Peace Institute, the Salzburg Global Seminar, the Rural Development Institute, the Trilateral Commission, Hubert H. Humphrey School of Public Affairs at the University of Minnesota, the Ruckleshaus Institute, the Burton K. Wheeler Center for Public Policy in Bozeman, Montana, and Yale President’s Council on International Activities.