Hans Ernst August Buchner (16 December 1850 – 5 April 1902) was a German bacteriologist who was born and raised in Munich.

He was the older brother of Eduard Buchner (1860–1917), winner of the 1907 Nobel Prize in Chemistry.

In 1880 he became a lecturer at the University of Munich, where in 1894 he succeeded Max von Pettenkofer (1818–1901) as professor and director of the institute of hygiene.

[2][3] Along with Martin Hahn, he assisted his brother, Eduard Buchner, with the isolation of zymase.

Their findings were published in a 1903 treatise titled "Die Zymasegärung" (Zymase fermentation).