Prince John Konstantinovich of Russia (d. 1918)

Prince John Constantinovich of Russia (Russian: Иоанн Константинович; 5 July 1886 – 18 July 1918), sometimes also known as Prince Ivan or Prince Johan, was the eldest son of Grand Duke Konstantin Konstantinovich of Russia by his wife, Yelizaveta Mavrikievna, née Princess Elisabeth of Saxe-Altenburg. He was described by contemporaries as a gentle, religious person, nicknamed "Ioannchik" by his relatives.