French catholic missionary, a member of the Holy Ghost Mission based at Zanzibar (Tanzania). Regarded as the greatest of the Swahili lexicographers, he was the first to write on the Swahili language. He produced his first Dictionnaire Français-Swahili locally in Africa in 1891 but it was not published in Paris until 1941. He follwed this landmark publication with a Swahili grammar (1909) and his Dictionnaire Swahili-Français (1939). His plant specimens were collected towards the end of the 19th century and it is probable that material interpreted as R.P. Sacleux refers to Rév. Père Sacleux. He is commemorated by a number of taxa including Allanblackia sacleuxii Hua, Barleria sacleuxii Benoist, Cucumis sacleuxii Pailleux & Bois and Tinnea sacleuxii Sprenger.