Marc-Antoine Parseval des Chênes (April 27, 1755 – August 16, 1836) was a French mathematician, most famous for what is now known as Parseval's theorem, which presaged the unitarity of the Fourier transform.
He was born in Rosières-aux-Salines, in France, into an aristocratic French family, and married Ursule Guerillot in 1795, but divorced her soon thereafter. A monarchist opposed to the French revolution, imprisoned in 1792, Parseval fled the country later for publishing poetry critical of the government of Napoleon.
Later, he was nominated to the Paris Academy of Sciences five times, from 1796 to 1828, but was never elected. His only mathematical publications were, apparently, five papers, published in 1806 as Mémoires présentés à l'Institut des Sciences, Lettres et Arts, par divers savants, et lus dans ses assemblées. Sciences mathématiques et physiques. (Savants étrangers.) This combined the following earlier monographs:
1. "Mémoire sur la résolution des équations aux différences partielles linéaires du second ordre," (May 5, 1798).
It was in the second, 1799, memoir in which he stated, but did not prove (claiming it to be self-evident), the theorem that now bears his name. He further expanded upon it in his 1801 memoir, and used it to solve various differential equations. The theorem was first printed in 1800 as a part (p. 377) of Traité des différences et des séries by Lacroix.
* Parseval, MacTutor History of Mathematics archive.