Sergei Kravchinski, known in 19th century London revolutionary circles as Stepniak, was the Russian who killed the chief of that country's secret police with a dagger in the streets of St Petersburg in 1878.

Stepniak had joined the rising against the Turks in Bosnia in 1876, and used that experience to write a manual on guerrilla warfare. He also joined the anarchist Errico Malatesta in his small rebellion in the Italian province of Benevento in 1877.