Sergei Stanislavovich Udaltsov is a Russian left-wing political activist. He is the unofficial leader of the Vanguard of Red Youth (AKM). In 2011 and 2012, he helped lead a series of protests against Vladimir Putin. In 2014 he was sentenced to 4¹⁄₂ years in a penal camp for organizing the May 2012 protest which ended in violence between the police and demonstrators.

The 2011–2013 Russian protests, which some English language media referred to as the Snow Revolution, began in 2011 and continued into 2012 and 2013. The protests were motivated by claims of Russian and foreign journalists, political activists and members of the public that the election process was fraudulent. The Central Election Commission of Russia stated 11.5% of official reports of fraud could be confirmed as true.