Ignác Martinovics (20 July 1755 – 20 May 1795) was a Hungarian philosopher, political adventurer, and a leader of the Hungarian Jacobin movement. He was condemned to death for high treason and beheaded on 20 May 1795, along with Count Jacob Sigray (Hungarian: Sigray Jakab), Ferenc Szentmarjay, Joseph Hajnoczy (Hungarian: Hajnóczy József), and others.
Martinovics's was of Serb origin, his father Mátyás Martinovics's family moved to Hungary in the late 17th century with the Great Migrations of the Serbs. Born in Pest, after finishing the first classes in a Piarist school, he chose to enter the Franciscan order. Martinovics took theological studies in the university of Buda from 1775-1779. From 1783 he was a teacher in natural sciences at the University of Lemberg.
Martinovics worked as a secret agent for the Austrian Emperor Leopold II until 1792. In his Oratio pro Leopoldo II he is explicit that only the authority that follows from a social contract should be recognized; he saw the aristocracy as the enemy of mankind, because they prevented people from becoming educated. In another of his works, Catechism of People and Citizens, he argued that citizens tend to oppose any repression and that sovereignty resides with the people. He became a Freemason. He was in favour of a federal republic for Hungary. A member of the Hungarian Jacobins, he was considered an idealistic forerunner of revolutionary thought by some, and an unscrupulous adventurer by others. He was in charge of stirring up a revolt against the nobility among the Hungarian serfs. Francis II, Holy Roman Emperor dismissed Martinovics and his boss, Ferenc Gotthardi, the former chief of the secret police, for these subversive acts. He was executed, together with 6 other prominent Jacobins, in Budapest on 20 May 1795.
A masonic lodge of Budapest belonging to the Hungarian Grand Orient is named after him.