Prince Frederick Charles Alexander of Prussia (German: Friedrich Karl Alexander; 29 June 1801 – 21 January 1883) was a younger son of Frederick William III of Prussia.
He served as a Prussian general for much of his adult life and became the first Herrenmeister (Grand Master) of the Order of Saint John after its restoration as a chivalric order.
Nevertheless, he is perhaps remembered more often for his patronage of art and for his sizable collections of art and armor.
Source: Stiftung Preußische Schlösser und Gärten Berlin-Brandenburg (Hrsg.): Sir Charles Glienicke. Porticus 2001, S. 10 License: CC-PD-Mark PD-Art (PD-old-100)