British trader and explorer who investigated the western tributaries of the Nile River and made zoological and ethnological discoveries in the Sudan and central Africa. He was the first European to encounter the Zande of the northeastern Congo River basin.

Petherick went to Africa in 1845 on a fruitless search for coal deposits in the interior of Egypt and the Sudan and remained in the Sudan as a trader. He later transferred his energies to the investigation of the tributaries of the Nile that run through the southern Sudan, notably the Baḥr-al-Ghazāl (Baḥr al-Ghazāl). In 1853 he reached the borders of the Zande nation. Following the publication of his accounts of his travels, Egypt, the Soudan and Central Africa (1861), the Royal Geographical Society appointed him to meet John H. Speke (Speke, John Hanning) and James A. Grant (Grant, James Augustus) on their return from discovering the source of the Nile. While carrying out further investigations in the Zande country, however, Petherick misjudged Speke's arrival and missed him.