Bulgarian Kings and Tsars: 2 tsars
Tsar Konstantin I   1257-1277  
Tsar Konstantin II   1397-1422  
Bulgarian Presidents and Prime Ministers: 2 prime ministers
(prime minister) Konstantin Stoilov   1887; 1894-1899  
(prime minister) Konstantin Muraviev   1944  
Estonian Presidents and Prime Ministers: 1 state elder/prime minister/president
(state elder/prime minister/president) Konstantin Päts   1921-1922; 1923-1924; 1931-1932; 1932-1933; 1933-1934; 1934-1937; 1938-1940  
Nobel Prize Winners: 1 physics
(physics) Konstantin Novoselov   2010  
Notable Actors and Entertainers: 3 actors
Konstantin Stanislavski   1863-1938  
Konstantin Lavronenko   1961-  
Costa Ronin   1979-  
Notable Athletes: 1 tennis
(tennis) Konstantin Kravchuk   1985-  
Notable Filmmakers: 1 director
Konstantin Stanislavski   1863-1938  
Notable Military Figures: 1 officer
Konstantin Rokossovsky   1896-1968  
Notable Scientists and Inventors: 1 engineer, 1 physicist
Konstantin Tsiolkovsky   1857-1935  
Konstantin Novoselov   1974-  
Olympic Medalists: 2 silver, 1 bronze, 1 bronze/gold/silver
(bronze/gold/silver) Elmer Niklander (a.k.a. Konstantin)   1912; 1920   discus throw - both hands; shot put - both hands; discus throw; shot put  
(silver) Konstantin Volkov   1980   pole vault  
(bronze) Konstantin Dubrovin   1996   swimming - 4x200 m freestyle relay  
(silver) Konstantin Ushkov   1996   swimming - 4x100 m freestyle relay  
Other Leaders: 1 general secretary
General Secretary Konstantin Chernenko   1984-1985   Soviet Union  
Russian Grand Dukes and Tsars: 1 duke
Duke Konstantin   1216-1218