The richest new entry to this year’s billionaire list is someone who has long stayed out of the spotlight—Marilyn Simons, widow of legendary hedge fund manager Jim Simons, has officially joined the elite ranks with a staggering net worth of $31 billion.

Known for her low-profile lifestyle and deep philanthropic commitment, Marilyn Simons has maintained a quiet presence despite overseeing one of the world’s largest fortunes. Her wealth stems primarily from her late husband’s investment empire, Renaissance Technologies, which revolutionized quantitative finance and generated unprecedented returns over decades.

While Jim Simons was widely celebrated as the “quant king,” Marilyn played a key role behind the scenes, especially in steering the family’s charitable foundation, which has donated hundreds of millions to education, science, and autism research.

Now recognized as the richest new billionaire of 2025, Marilyn Simons embodies a rare combination: enormous wealth with understated influence. Her entry into the billionaire list signals not only the enduring legacy of the Simons financial empire but also the quiet power held by some of the world’s most discreet philanthropists.