Constantin Freiherr von Ettingshausen (or Baron Constantin von Ettingshausen) (16 June 1826 in Vienna – 1 February 1897 in Graz) was an Austrian botanist known for his paleobotanical studies of flora from the Tertiary era. He was the son of physicist Andreas von Ettingshausen.^[1]

In 1848 he graduated as a doctor of medicine in Vienna, and became in 1854 a professor of botany and natural history at the medical and surgical military academy in that city. In 1871 he was chosen professor of botany at Graz, a position which he maintained until the close of his life.^[2]

From 1876 he made repeated visits to London, where he arranged collections at the Natural History Museum.^[3] He was distinguished for his researches on the Tertiary floras of various parts of Europe, and on the fossil floras of Australia and New Zealand.^[2] The extinct genus Ettingshausenia (family Vitaceae) was named in his honor by August Wilhelm Stiehler (1857).^[4][5]

• Physiotypia plantarum austriacarum (with Alois Pokorny), 1856 –.
• Physiographie der Medicinal Pflanzen (1862).
• Die Farnkruter der Jetztwelt zur Untersuchung and Bestimmung der in den Formationen der Erdrinde eingeschiossenen Uberreste von vorweltlichen Arten dieser Ordnung nach dem Flächen-Skelet bearbeitet (1865).
• A Monograph of the British Eocene Flora (with John Starkie Gardner), vol. 1. Filices, 1879-82. -- vol. 2. Gymnospermæ, by J. Gardner. 1883-86.
• Contributions to the Tertiary flora of Australia (translated by Arvid Neilson, 1888).
• Contributions to the knowledge of the fossil flora of New Zealand (translated by C. Juhl, 1890).^[6]

Regarding personal names: Freiherr is a former title (translated as Baron). In Germany since 1919, it forms part of family names. The feminine forms are Freifrau and Freiin.