
Jonas von Mahren (1232-1257) was a Palatine German nobleman who served as a general of the Teutonic Order during the 13th century. By 1253, he was in command of an army in Livonia. He established a fort to the south of Olysta to threaten Novgorod, but, in 1257, Grand Prince Alexander Nevski assaulted his fort at Grundas. Jonas and most of his men fought to the death, and the fort fell to the Russians after heavy fighting.