Oscar Baumann (June 25, 1864 in Vienna - October 12, 1899 in Vienna) was an Austrian cartographer with a keen interest in ethnography.
He attended classes on natural history and geography at the University of Vienna, and in 1885 was part of an Austrian exploratory expedition of the Congo Basin headed by Oskar Lenz. However, he had to leave the expedition early due to illness. In 1886 he did ethnographical research on the island of Fernando Po. When he returned to Europe, he obtained his PhD from the University of Leipzig in 1888.
Baumann is best known for his exploration of the interior of German East Africa (present-day Tanzania, Rwanda and Burundi), and producing maps of the region. In 1888 he explored the Usambara region with geographer Hans Meyer, with designs of continuing on to Mount Kilimanjaro. However, their progress was stopped due to ramifications associated with the so-called "Abushiri Revolt" (1888–89). Within a matter of days Baumann and Meyer were captured and held as prisoners, and only after a large ransom was paid to rebel leader Abushiri ibn Salim al-Harthi were the two men released.
Baumann's most celebrated mission was the 200-member "Maasai Expedition" of 1891-1893. On this trek, he performed map-making duties, and was the first European to visit Lake Eyasi, Lake Manyara and Ngorongoro Crater. As a result of the journey, he produced a book titled Durch Massailand zur Nilquelle (By Massailand to the Source of Nile) in 1894. In 1892, he became the first European to enter Rwanda.
In 1896, Baumann was appointed consul to Zanzibar by the Austro-Hungarian government. However, he died a few years later of an infectious disease at the age of 35. Today at the Vienna Museum of Ethnology are nearly 3500 artifacts that Baumann amassed from his African journeys. These include weapons, tools, jewellery, herbal perfumes and musical instruments.