Sir Leonard Valentinovich Blavatnik, commonly known as Len Blavatnik, is a Ukrainian-born British-American billionaire businessman, investor, and philanthropist. He is the billionaire founder of Access Industries, a privately held conglomerate he founded in 1986, headquartered in New York City with diverse investments spanning natural resources, media and entertainment, real estate, and biotechnology. Born on June 14, 1957, in Odesa, then part of the Ukrainian Soviet Socialist Republic within the Soviet Union, to a Jewish family, he moved with his parents to Yaroslavl, Russia, during his childhood. He began studies at the Moscow State University of Railway Engineering but did not complete his coursework as his family sought emigration visas amid rising antisemitism. Immigrating to the United States, he pursued higher education, earning a Master's degree in computer science from Columbia University in 1981 and an MBA from Harvard Business School in 1989. Blavatnik became a U.S. citizen in 1984 and a British citizen in 2010, and was knighted in 2017.

His business interests through Access Industries include significant stakes in companies like Warner Music Group and chemical giant LyondellBasell, contributing to his estimated net worth of $26.5 billion as of April 2025, ranking him among the world's richest individuals according to Forbes. His investment portfolio includes media, energy, and various other sectors.

Beyond business, Blavatnik is a noted philanthropist, supporting Jewish causes, education, and the arts; he has donated hundreds of millions to institutions like Harvard, Oxford, and Tel Aviv University. He serves as a patron of the arts, producing Broadway shows such as 'The Front Page' and 'Sunset Boulevard,' and maintains ties to organizations like Friends of the Israel Defense Forces. His influence extends through his media holdings and philanthropy, positioning him within networks of global finance, entertainment, and Jewish diaspora communities. His career reflects a journey from Soviet-era constraints to international prominence, marked by strategic investments and generous giving.