Karl Heinrich Ritthausen (13 January 1826 – 16 October 1912) was a German biochemist who identified two amino acids and made other contributions to the science of plant proteins.

Ritthausen was born in Armenruh, near Goldburg, Silesia, Prussia, in today's Poland.

He began to do research in Giessen with Justus von Liebig, and was inspired to continue investigation into agricultural chemistry.

The site of the experiment station became Poppelsdorf in 1867 when Ritthausen became professor of chemistry at University of Bonn.

These findings extended chemical awareness of functional groups in protein, and appeared in the Journal für Praktische Chemie.