Karl or Carl Philipp Sprengel (March 29, 1787 – April 19, 1859) was a German botanist from Schillerslage (now part of Burgdorf, Hanover).
Sprengel worked under Albrecht Thaer (1752–1828) in Celle. He then worked from 1804 to 1808 with Heinrich Einhof (1778–1808) in Möglin on agricultural studies. From 1821-1828 he studied natural sciences in Göttingen, where he eventually became professor. Sprengel died in Regenwalde (Resko), Pomerania.
Sprengel was the first to formulate the "theory of minimum" in agricultural chemistry, meaning that plant growth is limited by the essential nutrient at the lowest concentration. This rule, often incorrectly attributed to Justus von Liebig as Liebig's law of the minimum, was instead only popularised as a scientific concept by Liebig.