Ferdinand Johann Wiedemann (in Hapsal (now Haapsalu) – in Saint Petersburg)[1] was an Governorate of Estonia linguist who researched Uralic languages, mostly Estonian. Wiedemann was also a botanist.
Wiedemann was of German-Swedish origin. In 1869 he published an Estonian-German dictionary (Ehstnisch-deutsches Wörterbuch), which was the richest dictionary of Estonian words for a long time.