Events from the year 1840 in France.

• Monarch – Louis Philippe I

• 20 January - Dumont D'Urville discovers Adélie Land, Antarctica.
• 1 March - Adolphe Thiers becomes prime minister.
• 30 September - The frigate Belle Poule arrives in Cherbourg-en-Cotentin, returning the remains of Napoleon from Saint Helena. He is buried in Les Invalides.
• Metric system again mandatory across France.

• 11 February - Gaetano Donizetti's opera La Fille du Regiment premieres in Paris.

• 23 March -Louis-Émile Bertin, naval engineer (died 1924)
• 2 April - Émile Zola, novelist (died 1902)
• 22 April - Odilon Redon, painter and printmaker (died 1916)
• 13 May - Alphonse Daudet, novelist (died 1897)
• 20 October - Désiré-Magloire Bourneville, neurologist (died 1909)
• 12 November - Auguste Rodin, sculptor (died 1917)
• 14 November - Claude Monet, Impressionist painter (died 1926)^[1]
• 1 December - Marie Bracquemond, Impressionist painter (died 1916)

• 13 February - Nicolas Joseph Maison, Marshal of France and Minister of War (born 1770)
• 27 February - John Tessier, French Sulpician priest (born 1758)
• 22 March - Étienne Bobillier, mathematician (born 1798)
• 25 April - Siméon Denis Poisson, mathematician and physicist (born 1781)
• 7 June - Népomucène Lemercier, poet and dramatist (born 1771)
• 20 June - Pierre-Joseph Redouté, painter and botanist (born 1759)
• 7 September - Étienne-Jacques-Joseph-Alexandre MacDonald, Marshal of France (born 1765)