Baron Johan Mauritz Nordenstam was a Finnish general who served as Vice Chairman of the Economic Division of the Senate of Finland, an office preceding that of Prime Minister, from 1858 to his death in 1882. He was the longest-serving head of government in Finnish history. He also served as the governor of Uusimaa Province from 1847 to 1858, vice chancellor of the University of Helsinki from 1847 to 1855, and a senator without portfolio from 1848 to 1858. He briefly served as acting Governor-General five times, and was Lord Marshal (speaker) at the first three sessions of the Diet of Finland following 54 years without an assembly.