E sther Grether is a Swiss billionaire businesswoman and one of the world's most important and private art collectors. She and her late husband built their fortune through their company, Doetsch Grether, a diversified business with interests in pharmaceuticals and consumer brands. The core of her wealth, however, comes from a different and highly lucrative source: a massive, early stake in the Swiss watch giant, the Swatch Group.

She was an early investor in the company that would become the Swatch Group and has held onto her stake for decades, which has grown to be worth billions. While her business activities are very low-profile, she is renowned in the art world for her incredible and vast collection of 20th-century art. Her collection is said to include more than 600 pieces, with a particular focus on artists like Pablo Picasso, Paul Cézanne, and Francis Bacon. She is known for being intensely private and rarely, if ever, displays her collection publicly.