Namesakes
Belgian Prime Ministers:
1 prime minister
Léon Delacroix (a.k.a. Gustave) 1918-1920 
French Presidents and Prime Ministers:
1 president
(president) René Coty (a.k.a. Gustave) 1954-1959
Nobel Prize Winners:
1 literature, 1 physics
(literature) J. M. G. Le Clézio (a.k.a. Gustave) 2008
(physics) Michel Mayor (a.k.a. Gustave) 2019
Notable Artists:
2 painters, 1 architect, 1 engraver
Gustave Courbet 1819-1877
Gustave Doré 1832-1883
Alexandre Gustave Eiffel 1832-1923
Gustav-Adolf Mossa (a.k.a. Gustave) 1883-1971
Notable Musicians:
1 composer
Gustave Charpentier 1860-1956
Notable Scientists and Inventors:
1 astronomer
Michel Mayor (a.k.a. Gustave) 1942-
Notable Writers:
1 author, 1 playwright
Gustave Flaubert 1821-1880
Gustav-Adolf Mossa (a.k.a. Gustave) 1883-1971
Olympic Medalists:
2 bronze
(bronze) Gustave Cabaret 1908 archery - continental style 50 m
(bronze) Gustave Marinius Heiss 1932 fencing
Other Leaders:
1 president
President Gustave Ador 1919 Switzerland
Other Royalty:
1 king
Baudouin of Belgium (a.k.a. Gustave) 1951-1993 Belgium
Title Characters:
1 song
(song) Alexandre Gustave Eiffel 1991 Alec Eiffel