Namesakes
Adolf Eichmann
(a.k.a. Otto) (m) 1906-1962 
Notable Evildoers
Adolf Windaus
(a.k.a. Otto) (m) 1876-1959
Nobel Prize Winners 1928 (chemistry)
Notable Scientists and Inventors
Claus of the Netherlands
(a.k.a. Otto) (m) 1926-2002
Other Royalty 1980-2002 Netherlands (prince consort)
Dénes Berinkey
(a.k.a. Ottó) (m) 1871-1944
Hungarian Presidents and Prime Ministers 1919 (prime minister)
Ernst Otto Fischer
(m) 1918-2007
Nobel Prize Winners 1973 (chemistry)
Georg von Rosen
(a.k.a. Otto) (m) 1843-1923
Notable Artists
Heinrich Otto Wieland
(m) 1877-1957
Nobel Prize Winners 1927 (chemistry)
Herbert Schade
(a.k.a. Otto) (m) 1922-1994
Olympic Medalists 1952 5000 m (bronze)
Jens Otto Krag
(m) 1914-1978
Danish Prime Ministers 1962-1968; 1971-1972
Karel III
(a.k.a. Otto) (m) 1887-1922
Bohemian Kings 1916-1918
Austrian Dukes and Emperors (Karl I) 1916-1918
Saints (Karl of Austria)
Karl Lagerfeld
(a.k.a. Otto) (m) 1933-2019
Notable Artists
Károly IV
(a.k.a. Otto) (m) 1887-1922
Hungarian Kings and Queens 1916-1918
Otto I the Great
(m) 912-973
German Kings and Holy Roman Emperors 936-973
Otto II the Red
(m) 955-983
German Kings and Holy Roman Emperors 961-983
Otto III
(m) 980-1002
German Kings and Holy Roman Emperors 983-1002
Otto of Bamberg
(m) 1060-1139
Saints
Otto IV
(m) 1175-1218
German Kings and Holy Roman Emperors 1198-1215
Ottó III of Bavaria
(m) 1261-1312
Hungarian Kings and Queens 1305-1308
Otto the Merry
(m) 1301-1339
Austrian Dukes and Emperors 1330-1339
Otto of Greece
(m) 1815-1867
Other Royalty 1832-1862 Greece (king)
Otto
(m)
Hurricanes and Tropical Storms 2004 (storm)
Otto
(m)
Hurricanes and Tropical Storms 2010 (hurricane)
Otto
(m)
Hurricanes and Tropical Storms 2016 (hurricane)
Otto Blehr
(m) 1847-1927
Norwegian Prime Ministers 1921-1923
Otto Boffin
(m)
Tolkien's Characters
Ottó Boros
(m) 1929-1988
Olympic Medalists 1956; 1960; 1964 water polo (bronze/gold)
Otto Cordes
(m) 1905-1970
Olympic Medalists 1928; 1932 water polo (gold/silver)
Otto Diels
(m) 1876-1954
Nobel Prize Winners 1950 (chemistry)
Notable Scientists and Inventors
Otto Dix
(m) 1891-1969
Notable Artists
Otto Ender
(m) 1875-1960
Austrian Chancellors and Presidents 1930-1931 (chancellor)
Otto Fahr
(m) 1892-1969
Olympic Medalists 1912 swimming - 100 m backstroke (silver)
Otto Flick
(m)
Fictional Characters from Television 1982 'Allo 'Allo!
Otto Graham
(m) 1921-2003
Hall-of-Famers 1965 (football)
Notable Athletes (football)
Otto Hahn
(m) 1879-1968
Nobel Prize Winners 1944 (chemistry)
Notable Scientists and Inventors
Otto B. Halvorsen
(m) 1872-1923
Norwegian Prime Ministers 1920-1921; 1923
Otto Herschmann
(m) 1877-1942
Olympic Medalists 1896 swimming - 100 m freestyle (silver)
Otto Hesselbom
(m) 1848-1913
Notable Artists
Otto Liebe
(m) 1860-1929
Danish Prime Ministers 1920
Otto Loewi
(m) 1873-1961
Nobel Prize Winners 1936 (medicine)
Otto Fritz Meyerhof
(m) 1884-1951
Nobel Prize Winners 1922 (medicine)
Otto Mueller
(m) 1874-1930
Notable Artists
Otto Friedrich Müller
(m) 1730-1784
Notable Scientists and Inventors
Otto Neumann
(m) 1902-1990
Olympic Medalists 1928 4x400 m relay (silver)
Otto Neururer
(m) 1882-1940
Saints
Otto Nilsson
(m) 1879-1960
Olympic Medalists 1908 javelin throw (bronze)
Otto Preminger
(m) 1905-1986
Notable Filmmakers
Otto Rehhagel
(m) 1938-
Notable Athletes (soccer)
Otto Scheff
(m) 1889-1956
Olympic Medalists 1908 swimming - 400 m freestyle (bronze)
Otto Stern
(m) 1888-1969
Nobel Prize Winners 1943 (physics)
Notable Scientists and Inventors
Otto Stich
(m) 1927-2012
Swiss Presidents 1988; 1994
Otto Strandman
(m) 1875-1941
Estonian Presidents and Prime Ministers 1919; 1929-1931 (prime minister/state elder)
Otto Tief
(m) 1889-1976
Estonian Presidents and Prime Ministers 1944 (prime minister)
Otto Trieloff
(m) 1885-1967
Olympic Medalists 1908 medley relay (silver)
Otto von Bismarck
(m) 1815-1898
German Chancellors and Presidents 1871-1890 (chancellor)
Otto von Guericke
(m) 1602-1686
Notable Scientists and Inventors
Otto Wagner
(m) 1841-1918
Notable Artists
Otto Wahle
(m) 1879-1963
Olympic Medalists 1900; 1904 swimming - 1500 m freestyle; swimming - 200 m obstacle; swimming - 400 m freestyle (silver/bronze)
Otto Wallach
(m) 1847-1931
Nobel Prize Winners 1910 (chemistry)
Notable Scientists and Inventors
Otto Heinrich Warburg
(m) 1883-1970
Nobel Prize Winners 1931 (medicine)
Ruud van Feggelen
(a.k.a. Otto) (m) 1924-2002
Olympic Medalists 1948 water polo (bronze)
Tage Reedtz-Thott
(a.k.a. Otto) (m) 1839-1923
Danish Prime Ministers 1894-1897