Hans Friedrich Gadow (8 March 1855 – 16 May 1928) was a German ornithologist.
Gadow was born in Pomerania, the son of an inspector of the Prussian royal forests. He studied at the universities of Berlin, Jena and Heidelberg. At Jena he studied under Ernst Haeckel and at Heidelberg under the anatomist Karl Gegenbaur. After graduation, he travelled to the Natural History Museum in London at the request of Albert Günther, to work on the museum's Catalogue of Birds. Gadow also established the first new sequence of bird orders and families that departed from earlier works in being based on phylogenetic ideas derived from anatomical and morphological features. The sequence was continued with modification by Alexander Wetmore and James L. Peters. Gadow prepared Volume VIII on the titmice, shrikes and nuthatches, and Volume IX on the sunbirds and honeyeaters.
In 1884 Gadow succeeded Osbert Salvin as Curator of the Strickland Collection at Cambridge University, as well as being appointed Lecturer on the Morphology of Vertebrates. He became a member of the British Ornithologists' Union in 1881 and a fellow of the Royal Society in 1892. He married Clara Maud Paget, daughter of Sir George E. Paget.
In 1895 and 1896 Gadow and his wife made two journeys along northern Spain, from the Basque Country to Galicia. In 1897 Gadow published In Northern Spain, the book that gathered together the very interesting observations on geography, ethnography, and fauna and flora he had made.
Gadow's publications included Classification of the Vertebra (1898), a translation of Haeckel's work entitled The Last Link (1898) and the articles on anatomy in Alfred Newton's Dictionary of Birds.
Hans Friedrich Gadow is commemorated in the scientific names of three species of Mexican lizards: Anolis gadovii, Mesaspis gadovii, and Urosaurus gadovi.
Clara Maud Gadow is commemorated in the scientific name of one species of Mexican lizard, Sceloporus gadoviae.