Leon Petrażycki (Polish: Leon Petrażycki; Russian: Лев Ио́сифович Петражи́цкий, romanized: Lev Iosifovich Petrazhitsky; 13 April 1867 – 15 May 1931) was a Russian and Polish philosopher, legal scholar, and sociologist, deputy of the first State Duma of Russian Empire. He is considered an important forerunner of the sociology of law and the founder of St. Petersburg School of Philosophy of Law.