Max von Gruber (6 July 1853, Vienna – 16 September 1927, Berchtesgaden) was an Austrian scientist.
As a bacteriologist he discovered specific agglutination in 1896 with his English colleague Herbert Durham (Gruber-Widal-reaction). But his main interests were studying the hygiene and the sexual life.
Max von Gruber was the son of Ignaz Gruber (1803–1872), a general practitioner and the first specialist in otology in Austria, and publisher of a two-volume textbook on medical chemistry (1835). His brother was Franz von Gruber. He graduated from the Schottengymnasium in Vienna and studied medicine at the University of Vienna, receiving his medical doctorate in 1876. He then learned chemistry and physiology under Max von Pettenkofer (1818–1901) and Karl von Voit (1831–1908) in Munich and Karl Ludwig (1816–1895) in Leipzig. Also working under Pettenkofer was Hans Ernst August Buchner (1850–1902), who encouraged Gruber to concentrate on bacteriology.
Unlike some of the great names of the time, among them Carl Wilhelm Nägeli, Theodor Billroth (1829–1894), Ferdinand Cohn (1828–1898), and Robert Koch (1843–1910), Gruber recognized that bacteria possess a variability within limits partially determined by the culture medium. This theory was important for the differentiation of the categories of bacteria and gained significance for Gruber in his examinations of cholera vibrios, enabling him to distinguish them from other vibrios.