Moisey Yakovlevich Ostrogorsky (also Moisei Ostrogorski; Russian: Моисе́й Я́ковлевич Острого́рский, romanized: Moisey Yakovlevich Ostrogorskiy; Belarusian: Майсей Якаўлевiч Aстрaгорскi, romanized: Majsiej Jakaŭlievič Astrahorski; 1854 – 10 February 1921) was a Russian politician, political scientist, historian, jurist and sociologist. Along with Max Weber and Robert Michels, he is considered one of the founders of political sociology, especially in the field of theories about party systems and political parties. Ostrogorski noted that loyalty to parties is often comparable to loyalty to one's religion. He was a member of the First State Duma of the Russian Empire representing the Grodno province in 1906–1907.
