Frederik Christian Kielsen (7 February 1774 Copenhagen - 18 January 1850 Frederiksberg) was a Danish schoolmaster noted for editing and publishing a series of copiously illustrated books on natural history - Icones amphibiorum, Icones avium, Icones piscium, Icones vermium, Icones mammalium, Icones insectorum.
Frederik Christian was the son of Olufsen Kielsen, an organist at the Garrison Church in Copenhagen, and Valentine Margerithe Dresler. He was at a school in Elsinore until 1790 when he began studying surgery, but soon changed to Natural History. He became assistant teacher at the Metropolitan School in 1806 and senior teacher 1812. For financial reasons he left in 1819, and settled in Vordingborg and lectured at the Latin School in this city while his weakened vision allowed. In 1833 he moved back to Copenhagen and stayed there until his death. On 29 May 1808 he married Louise Charlotte Amalie Jacobsen (born 2 June 1789). He translated a number of German children's books dealing with nature, but was especially capable as teacher and author of Natural History textbooks. This science was still new in school curricula and its teaching was problematic. He translated the German Natural History of 1797 by Karl Philipp Funke (1752-1807), which was duly used by schools, and wrote a comprehensive textbook on systematics (1802-4) followed by a small 'Guide for Beginners' (1807). The latter remained in use by schools for an entire generation.