Jean Alexander Heinrich Clapier de Colongue

Jean Alexander Heinrich Clapier de Colongue (Ivan Petrovich de Collong; Иван Петрович де-Колонг; Johans Aleksandrs Heinrihs Klapje de Kolongs) (2 March 1838–26 May 1901) was a Baltic German marine engineer and founder of a theory of magnetic deviation for magnetic compasses, living and working in Imperial Russia.

Ivan Petrovich de Collong was born in 1839 in Dünaburg (now Daugavpils) into a Baltic German noble family originally of Franco-Portuguese origin. He studied at the Naval Academy in Saint Petersburg and from 1870 he worked there as a lecturer. Starting in 1878 he was head of the Navy's Main Hydrographical Administration. In 1875 he constructed deflector (a new type of compass baffle) and later improved upon its design.

De Collong was a Corresponding Member of the Russian Academy of Sciences (from 1896) and a Major-General of the Imperial Russian Navy. He was awarded the Lomonosov Prize of the Russian Academy of Sciences.