Esther Grether (née Kast) was a Swiss billionaire businesswoman, art collector, and heir. Born in Basel, Switzerland, in 1936, her fortune is tied to her late husband's health and beauty care products company, Doetsch Grether Group, which she inherited and ran for decades. The company's origins trace back to a pharmacy founded in Basel in 1899.

Grether's career began as a secretary at the Rhineland firm before she married her boss, Hans Grether. She inherited the company in 1975 upon his death and successfully continued to run the firm for more than thirty years, a rare feat for a woman in business at the time. Her immense wealth is secured by the stable, continuous profitability of the private health and wellness sector and her colossal art collection.

Esther Grether's career is defined by her effective management of the Doetsch Grether Group (brands like Grether's Pastilles and Neo Angin pastilles), and her strategic financial investments. She successfully diversified the business and maintained its global reach.

Her greatest personal legacy is her art collection, which is considered one of the most important private collections of 20th-century art. The collection reportedly includes more than 600 pieces, including works by masters like Pablo Picasso, Francis Bacon (including his Triptych, May–June 1973, which she bought for a record price in 1989), and Paul Cézanne. She was on the Swatch Group's board of directors from 1986 to 2014. She gradually withdrew from operational duties around 2014, and passed away in Basel on August 27, 2025, at the age of 89. Her legacy and assets are now overseen by her children.

Esther Grether's social impact is structural, stemming from the Doetsch Grether Group's role as a provider of essential health and wellness products. Her greatest structural contribution is cultural: her massive art collection has been exhibited several times at Basel's Kunstmuseum, ensuring public access to culturally significant works.

Her career provides an inspirational example of a non-executive family member who successfully managed a major industrial business for decades and became a global patron of modern art.

Esther Grether maintained the elegant, discreet style of a Swiss financial matriarch and art patron. Her attire was professional and elegant, reflecting her profound commitment to culture and business. Her life was defined by the security of her multi-billion dollar fortune, rooted in the stable health care and art markets.

Residing in Basel, Switzerland, her ultimate luxury was the autonomy to manage her unique portfolio and her long-term commitment to 20th-century art collecting.