Grand Duchy of Mecklenburg-Schwerin
Duke John Albert of Mecklenburg (; given names "John Albert Ernest Constantine Frederick Henry"; 8 December 1857 – 16 February 1920) was a member of the House of Mecklenburg-Schwerin who served as the regent of two states of the German Empire. Firstly from 1897 to 1901 he was regent of Grand Duchy of Mecklenburg-Schwerin for his nephew Frederick Francis IV, Grand Duke of Mecklenburg, and from 1907 to 1913 he was Regent of the Duchy of Brunswick.