Karl Friedrich Otto Ruß (January 14, 1833, Baldenburg – September 29, 1899, Berlin) was a Prussian pharmacist, aviculturist, author of bird-keeping books, and the founding editor of the world's first bird-fancier magazine Die Gefiederte Welt.
He received a doctorate from Rostock University in 1866 and worked briefly as a pharmacist but was forced to give up due to a laryngeal problem.
He had been interested in ornithology from a young age and wished to make knowledge more widely available and had been especially influenced by the work of Emil Adolf Rossmässler.
In 1879 he was concerned about the hunting of hares in Germany as they had suffered from bad climatic conditions leading to the death of many in the previous two seasons.
He died from a heart attack at his home in Belle Alliance Strasse, Berlin and was buried in the Holy Cross Cemetery, Berlin-Mariendorf.