Charles Eloi Demarquet (June 13, 1796 – February 26, 1870) was one of the principal aides-de-camp of Simón Bolívar (the first name is sometimes given only as "Eloy" or "Eloi"). Originally a French officer, he fought for Napoleon, probably at Waterloo, and may have lost three fingers in that battle. He joined Bolivar early enough to have been one of the principal figures mentioned at the Battle of Carabobo. In Ecuador, he made friends with Jean-Baptiste Boussingault, who later became a famous chemist and left memoirs which describe both his time in South America in general and his relations with Demarquet in particular: