German geologist, astronomer, and traveler who was the first European to circumnavigate and map Lake Chad. Overweg was also a member of a pioneering mission to open the Central African interior to regular trade routes from the north coast of the continent.

In 1849 Overweg joined an expedition, headed by the English explorer James Richardson, which was mounted by the British government for the purpose of opening commercial relations with the kingdoms of Central Africa. The expedition left Tripoli, in Libya, in the spring of 1850 and crossed the Sahara southward. Early in 1851 the group split up, and Overweg went on alone by way of Zinder (in present south-central Niger) to Kukawa (northeast Nigeria), where he joined Heinrich Barth (Barth, Heinrich) (q.v.), the expedition's scientist (and, after the death of Richardson, leader). The two spent 18 months exploring southward to Adamawa emirate (Nigeria) and the Benue River, around Lake Chad and to the southeast, till Overweg's death.