Louis Francoeur entered the College d'Harcourt at Navarre in 1790. From 1793 he served in the army. He entered the École Polytechnique in 1794 and in 1798 he taught an analysis course for Lacroix.
Francoeur carried on with both a military and an academic career. He was theoretically made a sub-lieutenant in the artillery in 1802. In 1804 he was appointed professor of mathematics at the École Polytechnique, then in 1805 he became professor of mathematics at the Lycée Charlemagne.
In 1808 he was made professor of mathematics at the Faculté des Sciences, a post he was to hold in addition to others until 1845.
The French, under Napoleon, fought inconclusive battles and campaigns in various parts of Spain and Portugal during 1809-10. Francoeur was sent on this Peninsular Campaign but he broke a leg in an accident with a carriage. During 1810 he spent four months in bed as a result of this accident.
In 1811 a comet appeared causing great interest with the public. Francoeur became interested in astronomy as a result of this comet. In 1816 he entered the Society which was to promote elementary instruction in schools. He later became secretary of the Society. Francoeur encouraged learning in schools and his he did his part writing books.
Francoeur is famed as a writer of texts, publishing his mechanics book Traité de mécanique élémentaire in 1800, an elementary course of mathematics in 1809 and an astronomy text in 1812. His other books include Cours complet de mathematique pures (1819) in two volumes, La goniométrie (1820), L'enseignment du dessin linéaire (1827), Astronomie practique (1830), Elements de technologie (1833), Géodésie (1835) and Traité d'arithmétique appliquée à la banque (1845).
From 1840 an illness curtailed his activities forcing him to retire from his chair in the Faculty of Sciences in 1845.