Gustav Adolf Fischer (March 3, 1848 – November 11, 1886, Berlin) was a German African explorer.
He was born at Barmen. In 1876 he accompanied Clemens Denhardt's expedition to Zanzibar, where he settled as a physician.
In the following year he explored Wituland and the southern Oromo country. In 1878 he continued his journey to Wapokomoland and along the Tana River to Massa.
With the support of the Geographical Society of Hamburg he visited the Maasai country in 1882 and penetrated from the mouth of the Pagani River to Lake Naivasha. The Maasai prevented him from advancing further. Equipped with funds by the brother of Wilhelm Junker, an explorer, who with Emin Pasha and Gaetano Casati had been lost in the equatorial provinces, he organized a relief expedition which, however, was compelled to return after reaching Lake Victoria. Shortly after his return to Germany in 1886 he died of a bilious fever contracted during his journey.
He is commemorated in the names of a number of animals, including Fischer's lovebird, Agapornis fischeri.
- Mehr Licht im dunkeln Weltteil (1885)
- Das Masai-Land (1885)
He also wrote articles for Zeitschrift für Ethnologie and for the Verhandlungen of the Hamburg Geographical Society.