Alexander I of Russia ( Russian : Александр I Павлович , Aleksandr I Pavlovich ) ( 23 December ( O.S. 12 December ) 1777 - 1 December ( O.S. 19 November ) 1825 ) , .
Alexander I of Russia ( Russian : Александр I Павлович , Aleksandr I Pavlovich ) ( 23 December ( O.S. 12 December ) 1777 - 1 December ( O.S. 19 November ) 1825 ) , also known as Alexander the Blessed ( Russian : Александр Благословенный , Aleksandr Blagoslovennyi ) was Emperor of Russia from 23 March 1801 to 1 December 1825 and the first Russian King of Poland from 1815 to 1825 .