Jacques Alexandre César Charles (November 12, 1746 – April 7, 1823) is a French inventor, scientist, mathematician, and balloonist.

Charles and the Robert brothers launch the world's first (unmanned) hydrogen-filled balloon in August 1783; then in December 1783, Charles and his co-pilot Nicolas-Louis Robert ascend to a height of about 1,800 feet (550 m) in a manned balloon.

Their pioneering the use of hydrogen for lift lead to this type of balloon being named a Charlière (as opposed to a Montgolfière which uses hot air).

Charles's law, describing how gases tend to expand when heated, is formulated by Joseph Louis Gay-Lussac in 1802, but he credites it to unpublished work by Jacques Charles.

Charles is elected to the Académie des Sciences, in 1793, and subsequently becomes professor of physics at the Conservatoire des Arts et Métiers.