Sergei Magnitsky, Ukrainian-Russian accountant and lawyer (b. 1972)
Sergei Leonidovich Magnitsky (Russian: Сергeй Леонидович Магнитский, IPA: [sʲɪrˈɡʲej lʲɪɐˈnʲidəvʲɪtɕ mɐɡˈnʲitskʲɪj]; 8 April 1972 – 16 November 2009) was a Ukrainian-born Russian tax advisor responsible for exposing corruption and misconduct by Russian government officials while representing client Hermitage Capital Management. His arrest in 2008 and subsequent death after eleven months in police custody generated international attention and triggered both official and unofficial inquiries into allegations of fraud, theft and human rights violations in Russia. His posthumous trial was the first in the Russian Federation.

Magnitsky alleged there had been large-scale theft from the Russian state, sanctioned and carried out by Russian officials. He was arrested and eventually died in prison seven days before the expiration of the one-year term during which he could be legally held without trial. In total, Magnitsky served 358 days in Moscow's Butyrka prison. He developed gall stones, pancreatitis, and a blocked gall bladder, and was denied medical care. A human rights council set up by the Kremlin found that he had been physically assaulted shortly before his death. His case became an international cause célèbre.The United States Congress and President Barack Obama enacted the Magnitsky Act at the end of 2012, barring those Russian officials believed to be involved in Magnitsky's death from entering the United States or using its banking system. In response, Russia condemned the Act and claimed Magnitsky was guilty of crimes. Nearly a dozen other nations, as well as the European Union, have subsequently implemented or considered Magnitsky legislation.

In early January 2013, the Financial Times wrote that "the Magnitsky case is egregious, well documented and encapsulates the darker side of Putinism."