William Felix Browder (born 23 April 1964) is an American-born British financier and political activist. He is the CEO and co-founder of Hermitage Capital Management, the investment advisor to the Hermitage Fund, which at a time was the largest foreign portfolio investor in Russia. The Hermitage Fund was founded in partnership with Republic National Bank, with $25 million in seed capital. The fund, and associated accounts, eventually grew to $4.5 billion of assets under management. In 1997, the Hermitage Fund was the best-performing fund in the world, up by 238%. Browder's primary investment strategy was shareholder rights activism. Browder took on large Russian companies such as Gazprom, Surgutneftegaz, Unified Energy Systems, and Sidanco. In retaliation, on 13 November 2005, Browder was refused entry to Russia, deported to the UK, and declared a threat to Russian national security.Eighteen months after Browder was deported, on 4 June 2007, Hermitage Capital's offices in Moscow were raided by twenty-five officers of Russia's Interior Ministry. Twenty-five more officers raided the Moscow office of Browder's American law firm, Firestone Duncan, seizing the corporate registration documents for Hermitage's investment holding companies. Browder assigned Sergei Magnitsky, head of the tax practice at Firestone Duncan, to investigate the purpose of the raid. Magnitsky discovered that while those documents were in the custody of the police, they had been used to fraudulently re-register Hermitage's holding companies to the name of an ex-convict. Magnitsky was subsequently arrested by Russian authorities and died in prison, having been denied proper medical treatment. The reregistration of the Hermitage holding companies was an intermediate step before the perpetrators used those companies to apply for a fraudulent $230 million (~$294 million in 2021) tax refund, awarded on 24 December 2007.After Magnitsky's death, Browder lobbied for Congress to pass the Magnitsky Act, a law to punish Russian human rights violators, which was signed into law in 2012 by President Barack Obama. In 2013, both Magnitsky and Browder were tried in absentia in Russia for tax fraud. Both men—Magnitsky had died four years prior—were convicted and sentenced to imprisonment. Interpol rejected Russian requests to arrest Browder, saying the case was political. In 2014, the European Parliament voted for sanctions against 30 Russians believed complicit in the Magnitsky case; this was the first time it had taken such action. On 21 October 2017, the Russian government attempted to place Browder on Interpol's arrest list of criminal fugitives, the fifth such request, which Interpol eventually rejected on 26 October 2017. After the initial request, Browder's visa waiver for the United States was automatically suspended. After a bipartisan protest by U.S. Congressional leaders, his visa waiver was restored the following day. While visiting Spain in May 2018, Browder was arrested by Spanish authorities on a new Russian Interpol warrant and transferred to an undisclosed Spanish police station. He was released two hours later, after Interpol confirmed that this was a political case.