Matthias Calonius (January 7, 1738 – September 13, 1817) was Finland's most renowned jurist. Born in Saarijärvi as a pastor's son, he studied at the Royal Academy of Turku. He went on to become a lecturer and then (in 1773) full professor at the Faculty of Law there, despite being too poor and lacking in family connections to ever obtain an academic title. He was also a member of the Supreme Court of Sweden in Stockholm and, after the Finnish War and Diet of Porvoo, procurator (chancellor of justice) with the Senate of the Grand Duchy of Finland.