Events from the year 1840 in Germany
- January 22 – Johann Friedrich Blumenbach, German anthropologist (b. 1752)
- March 2 – Heinrich Wilhelm Matthias Olbers (b. 1758), German astronomer.
- May 7 – Caspar David Friedrich, German artist (b. 1774)
- May 11 – Eduard Joseph d'Alton, German engraver and naturalist (b. 1772)
- May 14 – Carl Ludvig Engel, German-Finnish architect (b. 1778)
- June 7 – King Frederick William III of Prussia (b. 1770)
- July 4 – Karl Ferdinand von Gräfe (born 1787), German surgeon.
- July 6 – Johann Heinrich Ramberg, German painter and printmaker (b. 1763)
- July 23 – Carl Blechen, German painter, specializing in fantastic landscapes with demons and grotesque figures (b. 1798)
- August 25 – Karl Leberecht Immermann, German novelist, dramatist (b. 1796)[4]
Van der Kiste, John (2004), George III's Children (revised ed.), Stroud, United Kingdom: Sutton Publishing Ltd, ISBN 978-0-7509-3438-1