G wendolyn Sontheim Meyer is an American billionaire and an heiress to the Cargill fortune, one of the largest and most significant family fortunes in the world. She is the great-great-granddaughter of William W. Cargill, who founded the agribusiness giant in 1865. Cargill is the largest private company in the United States, with vast operations in commodity trading, food processing, and agricultural services.

The Cargill and MacMillan families have controlled the company for over 150 years. Gwendolyn inherited her stake from her father, and her branch of the family is one of the key shareholders. Like the other heirs of her generation, she is not involved in the day-to-day management of the company. She is a passionate and accomplished equestrian, specializing in the sport of cutting, and she owns a ranch in California. Her immense wealth is derived from her inherited stake in the enduring and sprawling family enterprise.