Karl Hermann Gustav Müller (7 May 1851–7 July 1925) was a German astronomer.
[1] Between 1880–82, he assisted Hermann Carl Vogel in building a catalog of stellar spectra.
[1] He led the German expedition to Hartford, Connecticut, to observe the transit of Venus in 1882.
In 1886, he began a collaboration with Paul Kempf to assemble the Potsdam Durchmusterung, which was a stellar catalogue of all stars in the northern hemisphere with a magnitude of 7.5 or brighter.
In 1918 he was elected to the Prussian Academy of Sciences, and he would also become an associate of the Royal Astronomical Society in England.